Decouple otlp/otlptrace/otlptracegrpc 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/otlptracegrpc package.

This is a follow up to #4397.

[codecov]

Codecov Report

Merging #4400 (f271a39) into main (58c9cf6) will decrease coverage by 0.2%.
The diff coverage is 81.0%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #4400     +/-   ##
=======================================
- Coverage   83.6%   83.5%   -0.2%     
=======================================
  Files        196     206     +10     
  Lines      15306   15982    +676     
=======================================
+ Hits       12811   13359    +548     
- Misses      2237    2344    +107     
- Partials     258     279     +21     

Files Changed	Coverage Δ
exporters/otlp/otlptrace/otlptracegrpc/client.go	92.5% <ø> (ø)
...trace/otlptracegrpc/internal/otlptracetest/data.go	0.0% <0.0%> (ø)
exporters/otlp/otlptrace/otlptracegrpc/options.go	76.4% <ø> (ø)
...otlptrace/otlptracegrpc/internal/otlpconfig/tls.go	62.5% <62.5%> (ø)
...e/otlptracegrpc/internal/otlptracetest/otlptest.go	62.5% <62.5%> (ø)
.../otlptracegrpc/internal/otlptracetest/collector.go	72.9% <72.9%> (ø)
...ace/otlptracegrpc/internal/otlptracetest/client.go	82.2% <82.2%> (ø)
...race/otlptracegrpc/internal/envconfig/envconfig.go	86.4% <86.4%> (ø)
...ace/otlptracegrpc/internal/otlpconfig/envconfig.go	89.5% <89.5%> (ø)
...trace/otlptracegrpc/internal/otlpconfig/options.go	93.5% <93.5%> (ø)
... and 2 more