[BUILD] Remove option WITH_OTLP

[ThomsonTan]

Fixes #1926, #2160.

Changes

Remove WITH_OTLP option and raise error on its definition as it causes confusions (see the above issues). Also make WITH_OTLP_GRPC as a plain option like WITH_OTLP_HTTP.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #2161 (fc1bbc9) into main (0eca570) will decrease coverage by 0.04%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2161      +/-   ##
==========================================
- Coverage   87.17%   87.13%   -0.04%     
==========================================
  Files         166      166              
  Lines        4777     4777              
==========================================
- Hits         4164     4162       -2     
- Misses        613      615       +2     

see 1 file with indirect coverage changes

[owent]

LGTM and thanks.

[marcalff]

LGTM, see a small fix on the doc.

Thanks for the fix.