lib: add trace-sigint APIs

[theanarkh]

trace-sigint command line option is useful for debugging the busy code, expose it as API for using at runtime, such as APM SDK.

• 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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.05%. Comparing base (049664b) to head (e8583be).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #59040      +/-   ##
==========================================
- Coverage   90.06%   90.05%   -0.01%     
==========================================
  Files         645      645              
  Lines      189130   189142      +12     
  Branches    37094    37097       +3     
==========================================
  Hits       170339   170339              
+ Misses      11511    11508       -3     
- Partials     7280     7295      +15     

Files with missing lines	Coverage Δ
lib/internal/process/pre_execution.js	90.90% <100.00%> (+0.16%)	⬆️
lib/internal/watchdog.js	89.65% <ø> (+15.07%)	⬆️

... and 19 files with indirect coverage changes

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