feat: alternative proposal for diagnostic channel

[Uzlopak]

Just for comparison

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.97561% with 39 lines in your changes are missing coverage. Please review.

Project coverage is 93.76%. Comparing base (e39a632) to head (554f6f0).
Report is 362 commits behind head on main.

Files	Patch %	Lines
lib/core/diagnostics.js	68.68%	31 Missing ⚠️
lib/web/fetch/diagnostics.js	89.87%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2857      +/-   ##
==========================================
+ Coverage   85.54%   93.76%   +8.21%     
==========================================
  Files          76       85       +9     
  Lines        6858    23424   +16566     
==========================================
+ Hits         5867    21964   +16097     
- Misses        991     1460     +469     

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[climba03003]

I believe the order is wrong.
start, asyncStart, end, asyncEnd is the same name as tracing channel and people expect similar function.

start means start of function.
end means end of function (at return).

asyncStart means start of callback.
asyncEnd means end of callback.
In fetch case, since it is a promise, I don't see how asyncStart and asyncEnd would fit in any case. Unless there is a interceptor.