lua: add healthchecking and file searchers exclusion

[adamgreloch]

Description

Adds opt-in main loop healthchecking useful for in-C-call hang detection. It also adds an opt-in exclusion of file searchers to further harden the interpreter

Motivation and Context

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (refactoring, style fixes, git/CI config, submodule management, no code logic changes)

How Has This Been Tested?

• Already covered by automatic testing.
• New test added: (add PR link here).
• Tested by hand on: host, nilee

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (list the PRs, preferably in merge-order).
• I will merge this PR by myself when appropriate.

[gemini-code-assist]

Summary of Changes

Hello @adamgreloch, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces significant enhancements to Lua's robustness and integration capabilities, primarily by adding an opt-in healthchecking mechanism for the main loop and providing a configurable way to handle unhandled panics more gracefully in multithreaded environments. These changes aim to improve the stability and diagnosability of Lua applications, especially when embedded in larger systems.

Highlights

• Opt-in Healthchecking: I've implemented an opt-in healthchecking mechanism for the Lua main loop. This feature is designed to detect hangs, particularly those occurring during long-running C-call executions, by allowing an external entity to query the Lua VM's responsiveness.
• MT-Safe Heartbeat API: To support the healthchecking, I've exposed new, thread-safe C API functions: lua_sendheartbeatrequest and lua_getheartbeatresponse. These functions enable external components to safely request and receive heartbeat responses from the Lua VM, facilitating robust hang detection.
• Configurable Panic Handling: I've added an opt-in feature that allows replacing the default abort() behavior with pthread_exit() when an unhandled Lua panic occurs. This is crucial for multithreaded applications, as it prevents the entire process from crashing due to a single thread's unhandled panic, allowing other threads to continue execution.
• Internal Name Clash Resolution: As part of these changes, I've resolved a potential name clash by renaming the internal priority array to lpriority in src/lparser.c. This prevents conflicts with priority() functions that might be included from sys/threads.h.

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[gemini-code-assist]

Code Review

The pull request introduces healthchecking and replaces abort() with pthread_exit() on panic. The review identifies a critical bug in the use of pthread_exit that leads to undefined behavior, and uninitialized variables in the health check feature. There are also recommendations to fix typos in comments.

[github-actions]

Unit Test Results

8 039 tests  ±0   7 515 ✅ ±0   41m 52s ⏱️ - 2m 1s
  479 suites ±0     524 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit ecfb6b2. ± Comparison against base commit 8b776e4.

♻️ This comment has been updated with latest results.