fix(wall): don't touch V8 handles in ~WallProfiler

[szegedi]

Fixes the 5.18.0 regression reported as DataDog/dd-trace-js#9891: terminating a worker thread with profiling enabled aborts the process.

FATAL ERROR: v8::HandleScope::CreateHandle() Cannot create a handle without a HandleScope

 4: v8::HandleScope::CreateHandle(v8::internal::Isolate*, unsigned long)
 5: dd::WallProfiler::~WallProfiler()          [dd_pprof.node]
 6: dd::WallProfiler::CleanupHook(void*)       [dd_pprof.node]
 7: node::CleanupQueue::Drain()
 8: node::Environment::RunCleanup()
 9: node::FreeEnvironment(node::Environment*)
10: node::worker::Worker::Run()

Cause

e0ce2c2 (#391), second commit — "Add the zero-out-internal-field logic to PCP too".

On its surface, this could be fixed by adding a HandleScope to ~WallProfiler, but it unfortunately doesn't fully fix the problem, because we can invoke ~WallProfiler through the WeakCallback of Nan::ObjectWrap. V8 docs say

When a weak callback is first invoked the embedders must Reset() the handle which triggered the callback. No other V8 API calls may be called in the first callback.

This is something we clearly violate here. Turns out V8 release build doesn't actually police this today, but where the holders die in the same GC nothing orders their weak callbacks before the profiler's, so Get() can materialize a Local to an already-condemned object and write its internal field.

And in the end, this code isn't needed: a PCP holder is reachable only through that profiler's cpedKey_. Another WallProfiler in the same isolate uses a different key object. The slot dies with the only thing that could have read it so it doesn't matter whether it's zero'd out or not. So this restores 5.17.0 behavior for PCP.

Extending the tests so they catch this

test-worker-threads.ts already terminates 100 workers, but worker2.ts never set a sample context so liveContextPtrHead_ was always empty and the faulting walk never ran. I've now extended it so that it establishes one sample context around the listener registration, so the frame holding it stays reachable until termination.

Jira: PROF-15797

[github-actions]

Overall package size

Self size: 2.53 MB
Deduped: 3.24 MB
No deduping: 3.24 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | pprof-format | 2.3.1 | 504.33 kB | 504.33 kB | | source-map | 0.8.0 | 185.66 kB | 185.66 kB | | node-gyp-build | 4.8.4 | 13.86 kB | 13.86 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}