[bastienfaivre]

This Pull Request closes #3442.

It changes the following:

• Adds Context::set_interrupt_flag(Option<Arc<AtomicBool>>). While the flag is set, the next loop iteration or function call fails with the new EngineError::Interrupted, which scripts can't catch. The flag can be set from another thread.
• Checks the flag next to the existing runtime limit checks (IncrementLoopIteration, check_runtime_limits).
• Adds tests for loops, calls, try/catch, native functions that call back into JS, resetting or removing the flag, and setting it from another thread.

Discussion

• The runtime limits can't stop these scripts: the loop count is kept per call frame, so a loop that calls a looping function, or recursion without loops, never reaches it.
• A native function that doesn't call back into JS, such as a regex match (RegExp execution lacks backtracking limit, allowing ReDoS #4643), runs to completion.
• Cost: one branch on an Option per check, plus a relaxed atomic load when a flag is set. Not benchmarked.
• EngineError isn't #[non_exhaustive], so the new variant is a breaking change.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	53,578	53,578	0
Passed	51,450	51,450	0
Ignored	1,648	1,648	0
Failed	480	480	0
Panics	0	0	0
Conformance	96.03%	96.03%	0.00%

Tested main commit: bfaa15a7d60d8c92370a423d4134ab19b1b1fae0
Tested PR commit: af87ffb5715146c3f1081f75e97f53e4725b16e5
Compare commits: bfaa15a...af87ffb

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 63.15%. Comparing base (6ddc2b4) to head (af87ffb).
⚠️ Report is 1086 commits behind head on main.

Files with missing lines	Patch %	Lines
core/engine/src/vm/mod.rs	85.71%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5650       +/-   ##
===========================================
+ Coverage   47.24%   63.15%   +15.91%     
===========================================
  Files         476      538       +62     
  Lines       46892    60620    +13728     
===========================================
+ Hits        22154    38285    +16131     
+ Misses      24738    22335     -2403     

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