feat: Refactor Duplicated Code of OTLP Exporter

[hanyuancheung]

Fix: part of #2641

• Refactor otlpconfig part from exporter/otlp/otlpmetric(otlptrace)/internal/ into exporter/otlp/internal/envconfig

[codecov]

Codecov Report

Merging #3189 (0d232df) into main (8c6e6c4) will decrease coverage by 0.0%.
The diff coverage is 90.9%.

❗ Current head 0d232df differs from pull request most recent head cc62a02. Consider uploading reports for the commit cc62a02 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3189     +/-   ##
=======================================
- Coverage   77.3%   77.3%   -0.1%     
=======================================
  Files        159     154      -5     
  Lines      11134   10984    -150     
=======================================
- Hits        8610    8494    -116     
+ Misses      2327    2297     -30     
+ Partials     197     193      -4     

Impacted Files	Coverage Δ
exporters/otlp/internal/envconfig/config.go	100.0% <ø> (ø)
...orters/otlp/otlpmetric/internal/otest/collector.go	7.2% <0.0%> (ø)
exporters/otlp/otlpmetric/otlpmetricgrpc/config.go	35.2% <47.3%> (ø)
exporters/otlp/otlptrace/otlptracegrpc/options.go	76.4% <78.9%> (ø)
exporters/otlp/internal/envconfig/options.go	81.7% <86.0%> (ø)
exporters/otlp/internal/envconfig/envconfig.go	98.3% <100.0%> (+2.7%)	⬆️
exporters/otlp/otlpmetric/otlpmetricgrpc/client.go	87.8% <100.0%> (ø)
exporters/otlp/otlpmetric/otlpmetrichttp/client.go	78.8% <100.0%> (ø)
exporters/otlp/otlpmetric/otlpmetrichttp/config.go	100.0% <100.0%> (ø)
exporters/otlp/otlptrace/otlptracegrpc/client.go	92.5% <100.0%> (ø)
... and 7 more

[MrAlias]

Closing, the duplicate files are not generated.