Add workflow spans for tagging the logs with step name

[Caio-Nogueira]

This is a proposal to add arbitrary step-related tags on console logs emitted from within workflow instances (more specifically, steps).

• Creates a new internal method on the WorkflowEntrypoint base class that the engine will call instead of run;
• captures the do method from the original step (passed as an rpc property) and patches it;
• patched do will wrap the original user-defined callback so that it emits user spans and stores current span key in async context
• handleLog attaches to the workflow step span if it exists in current async context

[codspeed-hq]

Merging this PR will not alter performance

✅ 70 untouched benchmarks
⏩ 129 skipped benchmarks¹

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_{Comparing caio/workflows-tracing (4b6707a) with main (f6d3ef0)}

Footnotes

1. 129 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[codecov-commenter]

Codecov Report

❌ Patch coverage is 8.29016% with 177 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.47%. Comparing base (8496472) to head (4b6707a).
⚠️ Report is 79 commits behind head on main.

Files with missing lines	Patch %	Lines
src/workerd/api/workers-module.c++	0.00%	118 Missing ⚠️
src/workerd/io/trace.c++	0.00%	31 Missing ⚠️
src/workerd/io/worker.c++	51.61%	14 Missing and 1 partial ⚠️
src/workerd/io/tracer.c++	0.00%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6088      +/-   ##
==========================================
- Coverage   70.55%   70.47%   -0.09%     
==========================================
  Files         409      409              
  Lines      109532   109863     +331     
  Branches    18038    18093      +55     
==========================================
+ Hits        77281    77422     +141     
- Misses      21441    21625     +184     
- Partials    10810    10816       +6     

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[jasnell]

Passing FunctionCallbackInfo is supported but not really idiomatic for the code base. Generally speaking we should try to pass jsg typemapped types (e.g. kj::String, etc)

[Caio-Nogueira]

FunctionCallbackInfo is part of the signature. I'm now deconstructing it so that we can extract the correctly typed values and use those instead

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[jasnell]

Unused?

[Caio-Nogueira]

Ultimately selfRef lets us access the run method on the user's subclass