Decouple otlp/otlptrace/otlptracehttp from otlp/internal and otlp/otlptrace/internal using gotmpl

[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/otlptrace/otlptracehttp package.

This is a follow up to #4397.

[codecov]

Codecov Report

Merging #4401 (c5893b3) into main (9ec9cea) will increase coverage by 0.0%.
The diff coverage is 84.6%.

Additional details and impacted files

@@          Coverage Diff           @@
##            main   #4401    +/-   ##
======================================
  Coverage   83.6%   83.6%            
======================================
  Files        186     196    +10     
  Lines      14629   15306   +677     
======================================
+ Hits       12240   12811   +571     
- Misses      2155    2237    +82     
- Partials     234     258    +24     

Files Changed	Coverage Δ
exporters/otlp/otlptrace/otlptracehttp/options.go	100.0% <ø> (ø)
...otlptrace/otlptracehttp/internal/otlpconfig/tls.go	62.5% <62.5%> (ø)
...e/otlptracehttp/internal/otlptracetest/otlptest.go	62.5% <62.5%> (ø)
.../otlptracehttp/internal/otlptracetest/collector.go	66.6% <66.6%> (ø)
...ace/otlptracehttp/internal/otlptracetest/client.go	82.2% <82.2%> (ø)
...race/otlptracehttp/internal/envconfig/envconfig.go	86.4% <86.4%> (ø)
...ace/otlptracehttp/internal/otlpconfig/envconfig.go	89.5% <89.5%> (ø)
...trace/otlptracehttp/internal/otlpconfig/options.go	90.0% <90.0%> (ø)
...lp/otlptrace/otlptracehttp/internal/retry/retry.go	98.3% <98.3%> (ø)
exporters/otlp/otlptrace/otlptracehttp/client.go	77.6% <100.0%> (+0.1%)	⬆️
... and 2 more

... and 1 file with indirect coverage changes