fix(cmake)!: only compile protos if asked - monitoring

[dbolduc]

Part of the work for #8022 and #12428

Stop compiling monitoring_protos. Only compile them if monitoring is requested.

Use the common ga grpc library helper for monitoring. Note that we can do this because the protos have the right name.

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This change is 

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.01% ⚠️

Comparison is base (af7e22c) 93.62% compared to head (243a66f) 93.61%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12463      +/-   ##
==========================================
- Coverage   93.62%   93.61%   -0.01%     
==========================================
  Files        2039     2039              
  Lines      180676   180676              
==========================================
- Hits       169153   169148       -5     
- Misses      11523    11528       +5     

see 6 files with indirect coverage changes

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[scotthart]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @dbolduc)