Add OtlpHttp{Signal}Exporter#toBuilder() methods

[jack-berg]

Related to #5642. If merged, I'll follow up with a PR to add the same to the OtlpGrpc{Signal}Exporters.

[codecov]

Codecov Report

Patch coverage: 95.23% and project coverage change: -0.01% ⚠️

Comparison is base (fab7d13) 91.32% compared to head (cd4a55f) 91.31%.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5652      +/-   ##
============================================
- Coverage     91.32%   91.31%   -0.01%     
- Complexity     4980     4986       +6     
============================================
  Files           554      554              
  Lines         14731    14761      +30     
  Branches       1376     1378       +2     
============================================
+ Hits          13453    13479      +26     
  Misses          884      884              
- Partials        394      398       +4     

Files Changed	Coverage Δ
...o/opentelemetry/sdk/common/export/RetryPolicy.java	100.00% <ø> (ø)
...ry/exporter/internal/http/HttpExporterBuilder.java	92.10% <85.71%> (-1.55%)	⬇️
...entelemetry/exporter/internal/TlsConfigHelper.java	88.88% <100.00%> (+1.79%)	⬆️
...rter/otlp/http/logs/OtlpHttpLogRecordExporter.java	81.81% <100.00%> (+4.04%)	⬆️
...lp/http/logs/OtlpHttpLogRecordExporterBuilder.java	91.42% <100.00%> (+0.51%)	⬆️
...rter/otlp/http/metrics/OtlpHttpMetricExporter.java	86.66% <100.00%> (+2.05%)	⬆️
...lp/http/metrics/OtlpHttpMetricExporterBuilder.java	95.74% <100.00%> (+0.18%)	⬆️
...exporter/otlp/http/trace/OtlpHttpSpanExporter.java	81.81% <100.00%> (+4.04%)	⬆️
...r/otlp/http/trace/OtlpHttpSpanExporterBuilder.java	91.42% <100.00%> (+0.51%)	⬆️

... and 2 files with indirect coverage changes

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[jack-berg]

@jkwatson WDYT? Would like to get the equivalent done for the grpc exporters before next release.

[jkwatson]

@jkwatson WDYT? Would like to get the equivalent done for the grpc exporters before next release.

no objection from me. These new public methods seem entirely reasonable.