Add otlploghttp transform package

[MrAlias]

Part of #5057

This does not include testing for Resource or Scope values. See #5192.

[codecov]

Codecov Report

Attention: Patch coverage is 94.61538% with 14 lines in your changes are missing coverage. Please review.

Project coverage is 84.3%. Comparing base (7da00d9) to head (663db5c).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #5191     +/-   ##
=======================================
+ Coverage   84.1%   84.3%   +0.1%     
=======================================
  Files        258     258             
  Lines      16713   16966    +253     
=======================================
+ Hits       14067   14305    +238     
- Misses      2352    2362     +10     
- Partials     294     299      +5     

Files	Coverage Δ
exporters/otlp/otlplog/otlploghttp/client.go	100.0% <100.0%> (+12.5%)	⬆️
exporters/otlp/otlplog/otlploghttp/exporter.go	83.3% <50.0%> (-8.4%)	⬇️
...otlp/otlplog/otlploghttp/internal/transform/log.go	95.2% <95.2%> (-4.8%)	⬇️

... and 1 file with indirect coverage changes

[pellared]

LGTM. Just one comment that I find worth addressing.

[XSAM]

We might need to move the implementation of transform to a shared place. But we can do that as parts of #5056

BTW, this PR seems to be assigned to a wrong project Go Auto Instrumentation: Beta (You might need to move it out of the project, I don't have the write permission of this project)