Merge bitcoin/bitcoin#34422: Update libmultiprocess subtree to be more stable with rust IPC client

8fe91f3719 test: Updates needed after bitcoin-core/libmultiprocess#240 (Ryan Ofsky)
b7ca3bf061 Squashed 'src/ipc/libmultiprocess/' changes from 1fc65008f7d..1868a84451f (Ryan Ofsky)
1fea3bae5c ipc, test: Add tests for unclean disconnect and thread busy behavior (Ryan Ofsky)

Pull request description:

  Includes:

  - https://github.com/bitcoin-core/libmultiprocess/pull/241
  - https://github.com/bitcoin-core/libmultiprocess/pull/240
  - https://github.com/bitcoin-core/libmultiprocess/pull/244
  - https://github.com/bitcoin-core/libmultiprocess/pull/245

  The main change is https://github.com/bitcoin-core/libmultiprocess/pull/240 which fixes issues with asynchronous requests (https://github.com/bitcoin/bitcoin/issues/33923) and unclean disconnects (https://github.com/bitcoin/bitcoin/issues/34250) that happen with the rust mining client. It also adds tests for these fixes which had some previous review in #34284 (that PR was closed to simplify dependencies between PRs).

  The changes can be verified by running `test/lint/git-subtree-check.sh src/ipc/libmultiprocess` as described in [developer notes](https://github.com/bitcoin/bitcoin/blob/master/doc/developer-notes.md#subtrees) and [lint instructions](https://github.com/bitcoin/bitcoin/tree/master/test/lint#git-subtree-checksh)

  Resolves #33923 and #34250

ACKs for top commit:
  Sjors:
    re-ACK 8fe91f3719
  janb84:
    reACK 8fe91f3719
  Eunovo:
    ACK 8fe91f3719

Tree-SHA512: 7e8923610502ebd8603bbea703f82178ab9e956874d394da3451f5268afda2b964d0eeb399a74d49c4123e728a14c27c0296118577a6063ff03b2b8203a257ce

test/functional/interface_ipc_mining.py

@@ -7,7 +7,7 @@ import asyncio
 import time
 from contextlib import AsyncExitStack
 from io import BytesIO
-import re
+import platform
 from test_framework.blocktools import NULL_OUTPOINT
 from test_framework.messages import (
     MAX_BLOCK_WEIGHT,
@@ -313,17 +313,15 @@ class IPCMiningTest(BitcoinTestFramework):
                 await mining.createNewBlock(ctx, opts)
                 raise AssertionError("createNewBlock unexpectedly succeeded")
             except capnp.lib.capnp.KjException as e:
-                if e.type == "DISCONNECTED":
-                    # The remote exception isn't caught currently and leads to a
-                    # std::terminate call. Just detect and restart in this case.
-                    # This bug is fixed with
-                    # https://github.com/bitcoin-core/libmultiprocess/pull/218
-                    assert_equal(e.description, "Peer disconnected.")
-                    self.nodes[0].wait_until_stopped(expected_ret_code=(-11, -6, 1, 66), expected_stderr=re.compile(""))
-                    self.start_node(0)
+                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_equal(e.description, "remote exception: std::exception: block_reserved_weight (0) must be at least 2000 weight units")
-                    assert_equal(e.type, "FAILED")
+                assert_equal(e.type, "FAILED")
 
         asyncio.run(capnp.run(async_routine()))