Merge bitcoin/bitcoin#34727: test: Add IPC wake-up test and reuse mining context

ad75b147b5 test: scale IPC mining wait timeouts by timeout_factor (Enoch Azariah)
e7a918b69a test: verify IPC error handling for invalid coinbase (Enoch Azariah)
63684d6922 test: move make_mining_ctx to ipc_util.py (Enoch Azariah)
4ada575d6c test: verify createNewBlock wakes promptly when tip advances (Enoch Azariah)

Pull request description:

  This is a follow-up to implement a couple of test improvements discussed in recent IPC PRs and issues.

  - adds a test to `interface_ipc_mining.py` to verify that `createNewBlock` wakes up immediately when the tip advances, rather than waiting for the cooldown timer to expire (https://github.com/bitcoin/bitcoin/pull/34184#discussion_r2842239399).
  - moves `make_mining_ctx` into `ipc_util.py` so it can be reused across the IPC tests instead of duplicating the setup code (https://github.com/bitcoin/bitcoin/pull/34422#discussion_r2852445430).
  - adds a test case to verify that providing an invalid coinbase to `submitSolution` returns a remote exception instead of crashing the node, closing the loop on the issue reported in #33341.
  - scales IPC wait timeouts using the test suite's `timeout_factor` to prevent spurious failures in heavily loaded CI environments, capping extended waits to avoid test runner hangs (bitcoin-core/libmultiprocess#253 (comment)).

  Closes #33341.

ACKs for top commit:
  Sjors:
    ACK ad75b147b5
  achow101:
    ACK ad75b147b5
  sedited:
    ACK ad75b147b5

Tree-SHA512: 812aa64c03657761f06707e6a15b8b435ab7c75717a6748a919fcbcae317128e18403b0c1bddd4cdad877d286e69db52389633e4012faaa656acc01939091719

test/functional/test_framework/ipc_util.py

@@ -10,9 +10,13 @@ from dataclasses import dataclass
 from io import BytesIO
 from pathlib import Path
 import shutil
+import platform
 from typing import Optional
 
 from test_framework.messages import CBlock
+from test_framework.util import (
+    assert_equal
+)
 
 # Test may be skipped and not have capnp installed
 try:
@@ -148,3 +152,21 @@ async def mining_get_coinbase_tx(block_template, ctx) -> CoinbaseTxData:
         requiredOutputs=[bytes(output) for output in template_capnp.requiredOutputs],
         lockTime=int(template_capnp.lockTime),
     )
+
+async def make_mining_ctx(self):
+    """Create IPC context and Mining proxy object."""
+    ctx, init = await make_capnp_init_ctx(self)
+    self.log.debug("Create Mining proxy object")
+    mining = init.makeMining(ctx).result
+    return ctx, mining
+
+def assert_capnp_failed(e, description_prefix):
+    if e.description == "remote exception: unknown non-KJ exception of type: kj::Exception":
+        # macOS + REDUCE_EXPORTS bug: Cap'n Proto fails to recognize
+        # its own exception type and returns a generic error instead.
+        # https://github.com/bitcoin/bitcoin/pull/34422#discussion_r2863852691
+        # Assert this only occurs on Darwin until fixed.
+        assert_equal(platform.system(), "Darwin")
+    else:
+        assert e.description.startswith(description_prefix), f"Expected description starting with '{description_prefix}', got '{e.description}'"
+    assert_equal(e.type, "FAILED")