Merge bitcoin/bitcoin#27944: test: various USDT functional test cleanups (27831 follow-ups)

9f55773a37 test: refactor: usdt_mempool: store all events (stickies-v)
bc43270450 test: refactor: remove unnecessary nonlocal (stickies-v)
326db63a68 test: log sanity check assertion failures (stickies-v)
f5525ad680 test: store utxocache events (stickies-v)
f1b99ac94f test: refactor: deduplicate handle_utxocache_* logic (stickies-v)
ad90ba36bd test: refactor:  rename inbound to is_inbound (stickies-v)
afc0224cdb test: refactor: remove unnecessary blocks_checked counter (stickies-v)

Pull request description:

  Various cleanups to the USDT functional tests, largely (but not exclusively) follow-ups to https://github.com/bitcoin/bitcoin/pull/27831#pullrequestreview-1491438045. Except for slightly different logging behaviour in "test: store utxocache events" and "test: log sanity check assertion failures", this is a refactor PR, removing unnecessary code and (imo) making it more readable and maintainable.

  The rationale for each change is in the corresponding commit message.

  Note: except for "test: store utxocache events" (which relies on its parent, and I separated into two commits because we may want the parent but not the child), all commits are stand-alone and I'm okay with dropping one/multiple commits if they turn out to be controversial or undesired.

ACKs for top commit:
  0xB10C:
    ACK 9f55773a37. Reviewed the code and ran the USDT interface tests. I stepped through the commits and think all changes are reasonable.

Tree-SHA512: 6c37a0265b6c26d4f9552a056a690b8f86f7304bd33b4419febd8b17369cf6af799cb87c16df35d0c2a1b839ad31de24661d4384eafa88816c2051c522fd3bf5

test/functional/interface_usdt_mempool.py

@@ -137,9 +137,7 @@ class MempoolTracepointTest(BitcoinTestFramework):
         """Add a transaction to the mempool and make sure the tracepoint returns
         the expected txid, vsize, and fee."""
 
-        EXPECTED_ADDED_EVENTS = 1
-        handled_added_events = 0
-        event = None
+        events = []
 
         self.log.info("Hooking into mempool:added tracepoint...")
         node = self.nodes[0]
@@ -148,9 +146,7 @@ class MempoolTracepointTest(BitcoinTestFramework):
         bpf = BPF(text=MEMPOOL_TRACEPOINTS_PROGRAM, usdt_contexts=[ctx], debug=0)
 
         def handle_added_event(_, data, __):
-            nonlocal event, handled_added_events
-            event = bpf["added_events"].event(data)
-            handled_added_events += 1
+            events.append(bpf["added_events"].event(data))
 
         bpf["added_events"].open_perf_buffer(handle_added_event)
 
@@ -165,7 +161,8 @@ class MempoolTracepointTest(BitcoinTestFramework):
         self.generate(node, 1)
 
         self.log.info("Ensuring mempool:added event was handled successfully...")
-        assert_equal(EXPECTED_ADDED_EVENTS, handled_added_events)
+        assert_equal(1, len(events))
+        event = events[0]
         assert_equal(bytes(event.hash)[::-1].hex(), tx["txid"])
         assert_equal(event.vsize, tx["tx"].get_vsize())
         assert_equal(event.fee, fee)
@@ -177,9 +174,7 @@ class MempoolTracepointTest(BitcoinTestFramework):
         """Expire a transaction from the mempool and make sure the tracepoint returns
         the expected txid, expiry reason, vsize, and fee."""
 
-        EXPECTED_REMOVED_EVENTS = 1
-        handled_removed_events = 0
-        event = None
+        events = []
 
         self.log.info("Hooking into mempool:removed tracepoint...")
         node = self.nodes[0]
@@ -188,9 +183,7 @@ class MempoolTracepointTest(BitcoinTestFramework):
         bpf = BPF(text=MEMPOOL_TRACEPOINTS_PROGRAM, usdt_contexts=[ctx], debug=0)
 
         def handle_removed_event(_, data, __):
-            nonlocal event, handled_removed_events
-            event = bpf["removed_events"].event(data)
-            handled_removed_events += 1
+            events.append(bpf["removed_events"].event(data))
 
         bpf["removed_events"].open_perf_buffer(handle_removed_event)
 
@@ -212,7 +205,8 @@ class MempoolTracepointTest(BitcoinTestFramework):
         bpf.perf_buffer_poll(timeout=200)
 
         self.log.info("Ensuring mempool:removed event was handled successfully...")
-        assert_equal(EXPECTED_REMOVED_EVENTS, handled_removed_events)
+        assert_equal(1, len(events))
+        event = events[0]
         assert_equal(bytes(event.hash)[::-1].hex(), txid)
         assert_equal(event.reason.decode("UTF-8"), "expiry")
         assert_equal(event.vsize, tx["tx"].get_vsize())
@@ -226,9 +220,7 @@ class MempoolTracepointTest(BitcoinTestFramework):
         """Replace one and two transactions in the mempool and make sure the tracepoint
         returns the expected txids, vsizes, and fees."""
 
-        EXPECTED_REPLACED_EVENTS = 1
-        handled_replaced_events = 0
-        event = None
+        events = []
 
         self.log.info("Hooking into mempool:replaced tracepoint...")
         node = self.nodes[0]
@@ -237,9 +229,7 @@ class MempoolTracepointTest(BitcoinTestFramework):
         bpf = BPF(text=MEMPOOL_TRACEPOINTS_PROGRAM, usdt_contexts=[ctx], debug=0)
 
         def handle_replaced_event(_, data, __):
-            nonlocal event, handled_replaced_events
-            event = bpf["replaced_events"].event(data)
-            handled_replaced_events += 1
+            events.append(bpf["replaced_events"].event(data))
 
         bpf["replaced_events"].open_perf_buffer(handle_replaced_event)
 
@@ -261,7 +251,8 @@ class MempoolTracepointTest(BitcoinTestFramework):
         bpf.perf_buffer_poll(timeout=200)
 
         self.log.info("Ensuring mempool:replaced event was handled successfully...")
-        assert_equal(EXPECTED_REPLACED_EVENTS, handled_replaced_events)
+        assert_equal(1, len(events))
+        event = events[0]
         assert_equal(bytes(event.replaced_hash)[::-1].hex(), original_tx["txid"])
         assert_equal(event.replaced_vsize, original_tx["tx"].get_vsize())
         assert_equal(event.replaced_fee, original_fee)
@@ -277,9 +268,7 @@ class MempoolTracepointTest(BitcoinTestFramework):
         """Create an invalid transaction and make sure the tracepoint returns
         the expected txid, rejection reason, peer id, and peer address."""
 
-        EXPECTED_REJECTED_EVENTS = 1
-        handled_rejected_events = 0
-        event = None
+        events = []
 
         self.log.info("Adding P2P connection...")
         node = self.nodes[0]
@@ -291,9 +280,7 @@ class MempoolTracepointTest(BitcoinTestFramework):
         bpf = BPF(text=MEMPOOL_TRACEPOINTS_PROGRAM, usdt_contexts=[ctx], debug=0)
 
         def handle_rejected_event(_, data, __):
-            nonlocal event, handled_rejected_events
-            event = bpf["rejected_events"].event(data)
-            handled_rejected_events += 1
+            events.append(bpf["rejected_events"].event(data))
 
         bpf["rejected_events"].open_perf_buffer(handle_rejected_event)
 
@@ -305,7 +292,8 @@ class MempoolTracepointTest(BitcoinTestFramework):
         bpf.perf_buffer_poll(timeout=200)
 
         self.log.info("Ensuring mempool:rejected event was handled successfully...")
-        assert_equal(EXPECTED_REJECTED_EVENTS, handled_rejected_events)
+        assert_equal(1, len(events))
+        event = events[0]
         assert_equal(bytes(event.hash)[::-1].hex(), tx["tx"].hash)
         # The next test is already known to fail, so disable it to avoid
         # wasting CPU time and developer time. See