Add server metrics to capture gRPC activity

[cbalci]

Can be used to:

• distinguish gRPC queries from Netty based ones
• track migrations from HTTP to gRPC
• etc.

observability

[codecov-commenter]

Codecov Report

Merging #10678 (7450776) into master (866c796) will decrease coverage by 56.42%.
The diff coverage is 0.00%.

@@              Coverage Diff              @@
##             master   #10678       +/-   ##
=============================================
- Coverage     70.25%   13.83%   -56.42%     
+ Complexity     6503      439     -6064     
=============================================
  Files          2108     2054       -54     
  Lines        113866   111423     -2443     
  Branches      17181    16895      -286     
=============================================
- Hits          79991    15411    -64580     
- Misses        28283    94754    +66471     
+ Partials       5592     1258     -4334     

Flag	Coverage Δ
integration1	?
integration2	?
unittests1	?
unittests2	13.83% <0.00%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
...a/org/apache/pinot/common/metrics/ServerMeter.java	0.00% <0.00%> (-100.00%)	⬇️
...che/pinot/core/transport/grpc/GrpcQueryServer.java	0.00% <0.00%> (-52.57%)	⬇️

... and 1661 files with indirect coverage changes

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