v8: add cpu profile APIs

[theanarkh]

Add CPU profile APIs.

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[addaleax]

Suggested change

	class JSONOutputStream : public v8::OutputStream {
	class JSONOutputStream final : public v8::OutputStream {

[addaleax]

Btw – we may want to use HeapSnapshotStream here? I know it requires a bit more setup, but it integrates nicely with existing stream primitives in Node.js

[theanarkh]

I think these are two issues in HeapSnapshotStream:

1. We should not delete the snapshot(which is created in worker) in main thread.
2. It will crash when the worker exits.

const worker = require('worker_threads');

const w = new worker.Worker("setInterval(() => {}, 100)", { eval: true})
w.on('online', async () => {
  const stream = await w.getHeapSnapshot()
  stream.on('data', () => {});
  // Crash
  w.terminate();
});

[szegedi]

Advocating for using CpuProfiler::Start and thus eliminating the need for users to invent names for the profiler sessions in order to use the API.

[codecov]

Codecov Report

❌ Patch coverage is 86.15385% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.95%. Comparing base (961554c) to head (1b66417).
⚠️ Report is 51 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_v8.cc	77.41%	2 Missing and 5 partials ⚠️
lib/v8.js	94.11%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #59429      +/-   ##
==========================================
+ Coverage   89.93%   89.95%   +0.01%     
==========================================
  Files         667      667              
  Lines      196775   196841      +66     
  Branches    38409    38422      +13     
==========================================
+ Hits       176977   177069      +92     
+ Misses      12247    12200      -47     
- Partials     7551     7572      +21     

Files with missing lines	Coverage Δ
src/node_v8.h	40.00% <ø> (ø)
lib/v8.js	99.02% <94.11%> (-0.35%)	⬇️
src/node_v8.cc	79.84% <77.41%> (-0.59%)	⬇️

... and 51 files with indirect coverage changes

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