Store sampling context in ContinuationPreservedEmbeddedData

[szegedi]

What does this PR do?:
Moves profiler's sampling context into the V8 isolate's ContinuationPreservedEmbeddedData (CPED.) In fact, moves it into a private symbol-keyed property within the object as Node.js from version 23 will store AsyncContextFrame objects in the CPED.

Motivation:
Before this change, we rely on async_hooks in dd-trace-js to update the sampling context on every context switch. It is both somewhat costly to do this on every async context switch and we should also migrate away from async hooks, as profiling is their last user, they'll be deprecated in Node, and they bring their own set of performance overhead by using them.

Additional Notes:
In an R&D week experiment, we concluded that this works. It was not clear whether:

• creating a HandleScope
• Invoking Global::Get to get a local for a symbol,
• invoking Isolate::GetContinuationPreservedEmbeddedData, and
• Invoking Object::Get on it with the symbol
  will work from a signal handler, but they do, provided we guard them with an explicit GC guard.

The code using this in dd-trace-js' wall.js sets the context on AsyncLocalStorage.{enterWith|run}, and the before callback of AsyncHooks.createHook. With CPED storage enabled, we can eliminate the before callback and "only" keep the AsyncLocalStorage.{enterWith|run} callbacks – they are the minimum amount of instrumentation needed for the feature to work correctly then.

This branch can be tested with the same-named branch in dd-trace-js.

Jira: PROF-11771

[datadog-datadog-prod-us1]

⚪ Code Quality Violation

Prop name (useCPED) doesn't match rule (is|has) (...read more)

Enforces a consistent naming pattern for boolean props.

The pattern is: "^(is|has)[A-Z]([A-Za-z0-9]?)+" to enforce is and has prefixes.

    

[github-actions]

Overall package size

Self size: 9.57 MB
Deduped: 9.94 MB
No deduping: 9.94 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | source-map | 0.7.4 | 226 kB | 226 kB | | pprof-format | 2.1.0 | 111.69 kB | 111.69 kB | | p-limit | 3.1.0 | 7.75 kB | 13.78 kB | | delay | 5.0.0 | 11.17 kB | 11.17 kB | | node-gyp-build | 3.9.0 | 8.81 kB | 8.81 kB |

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

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-05-16 14:25:07

Comparing candidate commit cc4fbd7 in PR branch szegedi/cped-context with baseline commit 55ac3fa in branch main.

Found 1 performance improvements and 0 performance regressions! Performance is the same for 90 metrics, 29 unstable metrics.

scenario:profiler-light-load-no-wall-profiler-24

• 🟩 cpu_user_time [-8.006ms; -1.237ms] or [-10.359%; -1.601%]