OTLPLog Exporter Should Not Percent Decode Header Keys When Parsing Headers

[zhihali]

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originally from #5623, at this PR https://github.com/open-telemetry/opentelemetry-go/pull/5705, I correct the otlpmetric and otlptrace, but didn't update the otlplog

This PR has updated the otlplog

[linux-foundation-easycla[bot]]

The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: zhihali / name: Zhihan Li (0f832b94f702f0400dff3c2eaff1f1a21751fe3f, d250d03cf19b7001163d17422e3876998de7accc)
• :white_check_mark: login: Zhihan-Li / name: Zhihan (59041d36e71da09841a26f9ba06aa2ef00a0a93e, 4dcb2f5dbb215dc4ade8aafe0cac2e4a08321549, 79fc58ec57c92a8b033e0d64f10a5adc62f568df)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 84.5%. Comparing base (b37e8a9) to head (d250d03).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #5792     +/-   ##
=======================================
- Coverage   84.5%   84.5%   -0.1%     
=======================================
  Files        272     272             
  Lines      22798   22826     +28     
=======================================
+ Hits       19282   19305     +23     
- Misses      3173    3176      +3     
- Partials     343     345      +2     

see 3 files with indirect coverage changes

[pellared]

@zhihali, are you still working in it?