stats/opentelemetry: Add CSM Plugin Option

[zasweq]

This PR adds support for the CSM Plugin Option, as speced in the design. The interface and the implementation live in OpenTelemetry's internal/. The next step is the usage of the CSM Plugin Option in OpenTelemetry and the global configuration.

RELEASE NOTES: N/A

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 80.53%. Comparing base (adf976b) to head (4290e3a). Report is 57 commits behind head on master.

:exclamation: Current head 4290e3a differs from pull request most recent head c56b06b

Please upload reports for the commit c56b06b to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7205      +/-   ##
==========================================
- Coverage   81.24%   80.53%   -0.72%     
==========================================
  Files         345      349       +4     
  Lines       33941    34063     +122     
==========================================
- Hits        27574    27431     -143     
- Misses       5202     5437     +235     
- Partials     1165     1195      +30     

see 34 files with indirect coverage changes

[dfawley]

Looks like you still need to exclude these tests from go1.20 runs, too.

[zasweq]

Argh yeah, I started that but forget to wrap it up/send it out. Working on it now.