test(o11y): verify gRPC spans can be disabled (1)

[haphungw]

This is the first of a sequence of integration test additions for gRPC observability.

Fixes #5266
Fixes #5268
Fixes #5269

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.79%. Comparing base (fec0152) to head (16d98a7).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5353   +/-   ##
=======================================
  Coverage   97.79%   97.79%           
=======================================
  Files         222      222           
  Lines       46349    46349           
=======================================
+ Hits        45326    45328    +2     
+ Misses       1023     1021    -2     

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