Deprecate the otlptrace/internal packages

[MrAlias]

Part of #3846

The initial idea for otlptrace/internal was to keep it around going forward after everything had been copied to the sub-modules. This was decided against last SIG meeting as publishing a deprecated package and then removing the package (i.e. stop publishing new packages) should provide the same use-case to users. With that goal, this PR does the following:

Stop generating and deprecate:

• otlptrace/internal/envconfig
• otlptrace/internal
• otlptrace/internal/otlpconfig
• otlptrace/internal/otlptracetest
• otlptrace/internal/retry

Stop generating (it is only used in otlptrace):

• otlptrace/internal/tracetransform

Note: otlptrace/internal/envconfig and otlptrace/internal/retry have not been released yet. They are still deprecated instead of removed so the soon-to-be-released other internal packages will not have cross-module dependencies in their last release and ultimately fix the issue for users that upgrade to their latest value.

[codecov]

Codecov Report

Merging #4425 (a1da462) into main (10d9038) will decrease coverage by 0.1%.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #4425     +/-   ##
=======================================
- Coverage   81.2%   81.2%   -0.1%     
=======================================
  Files        247     247             
  Lines      20006   20006             
=======================================
- Hits       16256   16254      -2     
- Misses      3407    3409      +2     
  Partials     343     343             

Files Changed	Coverage Δ
...ers/otlp/otlptrace/internal/envconfig/envconfig.go	86.4% <ø> (ø)
exporters/otlp/otlptrace/internal/header.go	100.0% <ø> (ø)
...rs/otlp/otlptrace/internal/otlpconfig/envconfig.go	89.5% <ø> (ø)
...ters/otlp/otlptrace/internal/otlpconfig/options.go	82.8% <ø> (ø)
...xporters/otlp/otlptrace/internal/otlpconfig/tls.go	62.5% <ø> (ø)
exporters/otlp/otlptrace/internal/retry/retry.go	98.3% <ø> (ø)
...tlp/otlptrace/internal/tracetransform/attribute.go	100.0% <ø> (ø)
...lptrace/internal/tracetransform/instrumentation.go	100.0% <ø> (ø)
...otlp/otlptrace/internal/tracetransform/resource.go	100.0% <ø> (ø)
...ers/otlp/otlptrace/internal/tracetransform/span.go	96.5% <ø> (ø)

... and 1 file with indirect coverage changes