Merge bitcoin/bitcoin#34562: ThreadPool follow-ups, proactive shutdown and HasReason dependency cleanup

408d5b12e8 test: include response body in non-JSON HTTP error msg (Matthew Zipkin)
9dc653b3b4 test: threadpool, add coverage for all Submit() errors (furszy)
ce2a984ee3 test: cleanup, use HasReason in threadpool_tests.cpp (l0rinc)
d9c6769d03 test: refactor, decouple HasReason from test framework machinery (furszy)
dbbb780af0 test: move and simplify BOOST_CHECK ostream helpers (Hodlinator)
3b7cbcafcb test: ensure Stop() thread helps drain the queue (seduless)
ca101a2315 test: coverage for queued tasks completion after interrupt (furszy)
bf2c607aaa threadpool: active-wait during shutdown (furszy)
e88d274430 test: add threadpool Start-Stop race coverage (furszy)
8cd4a4363f threadpool: guard against Start-Stop race (furszy)
9ff1e82e7d test: cleanup, block threads via semaphore instead of shared_future (l0rinc)

Pull request description:

  A few follow-ups to #33689, includes:

  1) `ThreadPool` active-wait during shutdown:
  Instead of just waiting for workers to finish processing tasks, `Stop()` now helps them actively.
  This speeds up the JSON-RPC and REST server shutdown, resulting in a faster node shutdown when many requests remain unhandled. This wasn't included in the original PR due to the behavior change this introduces.

  2) Decouple `HasReason` from the unit test framework machinery
  This avoids providing the entire unit test framework dependency to low-level tests that only require access to the `HasReason` utility class. Examples are: `reverselock_tests.cpp`, `sync_tests.cpp`, `util_check_tests.cpp`, `util_string_tests.cpp`, `script_parse_tests.cpp` and `threadpool_tests.cpp`. These tests no longer gain access to unnecessary components like the chainstate, node context, caches, etc. It includes l0rinc's `threadpool_tests.cpp` `HasReason` changes.

  3) Include response body in non-JSON HTTP error messages
  Straight from pinheadmz [comment](https://github.com/bitcoin/bitcoin/pull/33689#discussion_r2783817192), it makes debugging CI issues easier.

ACKs for top commit:
  maflcko:
    review ACK 408d5b12e8 🕗
  achow101:
    ACK 408d5b12e8
  hodlinator:
    re-ACK 408d5b12e8

Tree-SHA512: 57aa0ef96886f32bf95a0bd7f87c878d31c9df9e34cb96de615eee703ce0824b5cfdf8f5c9cd19a3594559994295b5810c38c94f5efd6291cbbd83a95473357a

test/functional/test_framework/authproxy.py

@@ -191,7 +191,7 @@ class AuthServiceProxy():
         content_type = http_response.getheader('Content-Type')
         if content_type != 'application/json':
             raise JSONRPCException(
-                {'code': -342, 'message': 'non-JSON HTTP response with \'%i %s\' from server' % (http_response.status, http_response.reason)},
+                {'code': -342, 'message': f"non-JSON HTTP response with \'{http_response.status} {http_response.reason}\' from server: {http_response.read().decode()}"},
                 http_response.status)
 
         data = http_response.read()