Decouple otlp/otlpmetric/otlpmetrichttp from otlp/internal and otlp/otlpmetric/internal using gotmp

[MrAlias]

Currently the otlp exporters share internal packages across package boundaries. This is something we want to stop doing: #3846. This PR addresses the cross-module internal package use for the otel/exporters/otlp/otlpmetric/otlpmetrichttp package.

This is the second PR in accomplishing #4403. The only thing left will be to deprecate otlpmetric/internal.

[codecov]

Codecov Report

Merging #4407 (57e5827) into main (ac6cd49) will increase coverage by 0.1%.
The diff coverage is 85.4%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #4407     +/-   ##
=======================================
+ Coverage   83.2%   83.4%   +0.1%     
=======================================
  Files        218     229     +11     
  Lines      17460   18645   +1185     
=======================================
+ Hits       14538   15553   +1015     
- Misses      2629    2773    +144     
- Partials     293     319     +26     

Files Changed	Coverage Δ
exporters/otlp/otlpmetric/otlpmetrichttp/config.go	85.7% <ø> (ø)
...porters/otlp/otlpmetric/otlpmetrichttp/exporter.go	83.0% <ø> (ø)
...lp/otlpmetric/otlpmetrichttp/internal/oconf/tls.go	35.7% <35.7%> (ø)
...pmetric/otlpmetrichttp/internal/otest/collector.go	53.8% <53.8%> (ø)
...ric/otlpmetrichttp/internal/envconfig/envconfig.go	86.4% <86.4%> (ø)
...tlpmetric/otlpmetrichttp/internal/oconf/options.go	86.9% <86.9%> (ø)
...pmetric/otlpmetrichttp/internal/oconf/envconfig.go	92.0% <92.0%> (ø)
...otlpmetric/otlpmetrichttp/internal/otest/client.go	97.1% <97.1%> (ø)
.../otlpmetric/otlpmetrichttp/internal/retry/retry.go	98.3% <98.3%> (ø)
exporters/otlp/otlpmetric/otlpmetrichttp/client.go	78.7% <100.0%> (+0.1%)	⬆️
... and 4 more

... and 1 file with indirect coverage changes