stats/opentelemetry/csm: Get mesh_id local label from "CSM_MESH_ID" environment variable, rather than parsing from bootstrap file

[zasweq]

This PR switches the mesh_id local label to get set from the CSM_MESH_ID environment variable, with the same logic as other labels set from the environment. It no longer comes from the bootstrap, or needs to be parsed from the node_id of the bootstrap.

RELEASE NOTES:

• stats/opentelemetry/csm: Get mesh_id local label from "CSM_MESH_ID" environment variable, rather than parsing from bootstrap file

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.09%. Comparing base (ad81c20) to head (7a731cb).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7740      +/-   ##
==========================================
+ Coverage   82.07%   82.09%   +0.02%     
==========================================
  Files         362      362              
  Lines       28116    28116              
==========================================
+ Hits        23075    23081       +6     
- Misses       3839     3842       +3     
+ Partials     1202     1193       -9     

see 19 files with indirect coverage changes

[purnesh42H]

stats/opentelemetry/csm: Get mesh_id local label from "CSM_MESH_ID" environment variable, rather than parsing from bootstrap file

Not fully familiar with the background on this but for now should we keep both parsing from bootstrap and env var for backward compatibility?

[zasweq]

No not in this case, as we are getting rid of the old way entirely.

[zasweq]

Interop tests passed.