net: increase inbound capacity for block-relay-only connections

..and adjust the eviction logic.
The new default max connection number is 200, the default maximum of tx-relaying
inbounds is limited to 50% of all inbound connections.
With 11 outbound connections, that is (200 - 11) * 0.5 = 94.5.
As a result, the tx-related maximum traffic should not change
drastically.

When we receive an inbound connection and don't have space for another
full-relay peer, we now attempt to evict specifically a full-relay inbound
after receiving the version message of the new peer.

Once this commit is widely deployed, the added inbound capacity will
allow us to increase the number of outgoing block-relay-only connections.

Co-authored-by: Amiti Uttarwar <amiti@uttarwar.org>

test/functional/interface_usdt_net.py

@@ -35,8 +35,8 @@ MAX_MSG_DATA_LENGTH = 150
 # from net_address.h
 NETWORK_TYPE_UNROUTABLE = 0
 # Use in -maxconnections. Results in a maximum of 21 inbound connections
-MAX_CONNECTIONS = 32
-MAX_INBOUND_CONNECTIONS = MAX_CONNECTIONS - 10 - 1  # 10 outbound and 1 feeler
+MAX_CONNECTIONS = 53
+MAX_INBOUND_CONNECTIONS = 21 # 10 outbound and 1 feeler, (MAX_CONNECTIONS - 10 - 1) / 2 slots for tx-relaying inbounds
 
 net_tracepoints_program = """
 #include <uapi/linux/ptrace.h>

test/functional/p2p_eviction.py

@@ -45,10 +45,12 @@ class SlowP2PInterface(P2PInterface):
 class P2PEvict(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 1
-        # The choice of maxconnections=32 results in a maximum of 21 inbound connections
-        # (32 - 10 outbound - 1 feeler). 20 inbound peers are protected from eviction:
+        # The choice of maxconnections=53 results in a maximum of 21 tx-relaying inbound connections
+        # (53 - 10 outbound - 1 feeler) * 0.5 = 21. The other inbound slots are reserved for block-relay-only
+        # peers that don't play a role in this test.
+        # 20 inbound peers are protected from eviction:
         # 4 by netgroup, 4 that sent us blocks, 4 that sent us transactions and 8 via lowest ping time
-        self.extra_args = [['-maxconnections=32']]
+        self.extra_args = [['-maxconnections=53']]
 
     def run_test(self):
         protected_peers = set()  # peers that we expect to be protected from eviction

test/functional/p2p_opportunistic_1p1c.py

@@ -76,7 +76,7 @@ class PackageRelayTest(BitcoinTestFramework):
         self.setup_clean_chain = True
         self.num_nodes = 1
         self.extra_args = [[
-            "-maxmempool=5",
+            "-maxmempool=5","-maxconnections=150"
         ]]
 
     def create_tx_below_mempoolminfee(self, wallet, utxo_to_spend=None):