[pdata] Rename RegiserServer funcs to RegiserGRPCServer

[dmitryax]

p[log|trace|metric]otlp packages don't have grpc part in it anymore, so we need to add GRPC part to the related methods.

This change should've been landed in #6165

[codecov]

Codecov Report

Base: 91.77% // Head: 91.77% // No change to project coverage 👍

Coverage data is based on head (abaafdd) compared to base (c8871dc).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6182   +/-   ##
=======================================
  Coverage   91.77%   91.77%           
=======================================
  Files         218      218           
  Lines       13358    13358           
=======================================
  Hits        12259    12259           
  Misses        870      870           
  Partials      229      229           

Impacted Files	Coverage Δ
pdata/plog/plogotlp/logs.go	51.06% <100.00%> (ø)
pdata/pmetric/pmetricotlp/metrics.go	55.81% <100.00%> (ø)
pdata/ptrace/ptraceotlp/traces.go	51.06% <100.00%> (ø)
receiver/otlpreceiver/otlp.go	87.58% <100.00%> (ø)

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