[Mono] Fix wait's returning false on non-runtime queued user APC's.

[lateralusX]

Mono's internal interrupt handling uses user APC to break waits in case runtime needs to interrupt threads. If that happens, wait will return false. For API's like ManualResetEventSlim.Wait() with void return, this can cause issues if the wait is broken prematurely. If a user APC have been queued to the thread, not triggered by internal runtime interrupt handling, it would lead to unexpected side effects.

Fix makes sure runtime ignores returns from WaitForSingleObjectEx/WaitForMultipleObjectsEx due to APC completions not initialized by runtime.

Fix also adds a new runtime test to trigger this scenario for Mono runtime on Windows.

Fixes #115178.

[Copilot]

Pull Request Overview

This PR ensures that waits aren’t broken by non-runtime queued user APCs in Mono on Windows and adds a new regression test for this scenario.

• Introduce a new isolated test project and test (115178) to validate user APC behavior.
• Change mono_win32_leave_* functions to return a boolean flag and update their implementations.
• Update win32_wait_for_single_object_ex and win32_wait_for_multiple_objects_ex to loop on WAIT_IO_COMPLETION, adjust timeouts, and ignore non-runtime APCs.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/tests/baseservices/threading/regressions/115178/115178.csproj	Add a process-isolated test project for the new regression.
src/tests/baseservices/threading/regressions/115178/115178.cs	Implement new regression test for user APC–interrupted waits.
src/mono/mono/utils/mono-threads.h	Change prototypes of leave functions to return gboolean.
src/mono/mono/utils/mono-threads-windows.c	Update leave implementations to return alert status.
src/mono/mono/utils/mono-os-wait-win32.c	Add looping logic around WAIT_IO_COMPLETION and time accounting.

Comments suppressed due to low confidence (1)

src/mono/mono/utils/mono-os-wait-win32.c:65

• [nitpick] The enter-wait macro uses 'interrupted' but the leave-wait uses 'alerted'; consider unifying on one term (e.g. 'alerted') to reduce cognitive load.

gboolean interrupted = FALSE;