Add OtlpGrpc{Signal}Exporter#toBuilder() methods

[jack-berg]

Continuation of #5652.

Resolves #5642.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (a9b285d) 91.32% compared to head (6ea11c1) 91.32%.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #5680   +/-   ##
=========================================
  Coverage     91.32%   91.32%           
- Complexity     4988     4995    +7     
=========================================
  Files           554      554           
  Lines         14765    14789   +24     
  Branches       1378     1379    +1     
=========================================
+ Hits          13484    13506   +22     
- Misses          883      884    +1     
- Partials        398      399    +1     

Files Changed	Coverage Δ
...ry/exporter/internal/grpc/GrpcExporterBuilder.java	98.88% <100.00%> (+0.17%)	⬆️
.../exporter/otlp/logs/OtlpGrpcLogRecordExporter.java	81.81% <100.00%> (+4.04%)	⬆️
...er/otlp/logs/OtlpGrpcLogRecordExporterBuilder.java	92.68% <100.00%> (+0.37%)	⬆️
.../exporter/otlp/metrics/OtlpGrpcMetricExporter.java	86.66% <100.00%> (+2.05%)	⬆️
...er/otlp/metrics/OtlpGrpcMetricExporterBuilder.java	100.00% <100.00%> (ø)
...etry/exporter/otlp/trace/OtlpGrpcSpanExporter.java	81.81% <100.00%> (+4.04%)	⬆️
...porter/otlp/trace/OtlpGrpcSpanExporterBuilder.java	92.68% <100.00%> (+0.37%)	⬆️

... and 1 file with indirect coverage changes

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