WIP: migrate tracing from OpenCensus to OpenTelemetry

[Fedosin]

Fixes #

Proposed Changes

Release Note

[knative-prow]

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[codecov]

Codecov Report

Attention: Patch coverage is 38.07947% with 187 lines in your changes missing coverage. Please review.

Project coverage is 80.29%. Comparing base (589b6ab) to head (ab84c3b).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/tracingotel/setup.go	0.00%	80 Missing ⚠️
pkg/tracingotel/otel.go	34.00%	61 Missing and 5 partials ⚠️
pkg/queue/sharedmain/main.go	0.00%	20 Missing ⚠️
pkg/tracingotel/config/tracing.go	79.16%	10 Missing and 5 partials ⚠️
pkg/activator/handler/handler.go	80.00%	3 Missing and 1 partial ⚠️
pkg/queue/sharedmain/handlers.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15884      +/-   ##
==========================================
- Coverage   80.91%   80.29%   -0.62%     
==========================================
  Files         210      214       +4     
  Lines       16731    17007     +276     
==========================================
+ Hits        13538    13656     +118     
- Misses       2842     2992     +150     
- Partials      351      359       +8     

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[dprotaso]

/hold

I'm writing a feature track for this migration - should have something next week