Add OpenTelemetry exporter implementation

[sfleen]

This mirrors and duplicates most of the logic from the existing OpenCensus exporter to keep the functionality as similar as possible. Setting up the proxy to use this exporter will come in a follow-up.

#10111

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 85 lines in your changes missing coverage. Please review.

Project coverage is 67.91%. Comparing base (96124bc) to head (f143524).
Report is 455 commits behind head on main.

Files with missing lines	Patch %	Lines
linkerd/opentelemetry/src/lib.rs	0.00%	66 Missing ⚠️
linkerd/opentelemetry/src/metrics.rs	0.00%	19 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3215      +/-   ##
==========================================
+ Coverage   67.68%   67.91%   +0.23%     
==========================================
  Files         332      362      +30     
  Lines       15158    16854    +1696     
==========================================
+ Hits        10259    11447    +1188     
- Misses       4899     5407     +508     

Files with missing lines	Coverage Δ
linkerd/opentelemetry/src/metrics.rs	0.00% <0.00%> (ø)
linkerd/opentelemetry/src/lib.rs	0.00% <0.00%> (ø)

... and 44 files with indirect coverage changes

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