[MAINTAINER DOC] Define and document a deprecation process

[marcalff]

Fixes #1893
Fixes #1892

Changes

This change contains:

• Documentation for the new deprecation process,
• Supporting CMake options for the verification build documented in the process,
• Changed in CI to build the MAINTAINER_MODE code without deprecated items.

Also, it contains the actual deprecation for the Jaeger Exporter:

• CMake changes to deprecate WITH_JAEGER,
• C++ changes in headers to deprecate all jaeger related code,
• Entries in DEPRECATED.md to document the jaeger exporter deprecation.

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 #1923 (cda221a) into main (65ebdb1) will decrease coverage by 0.02%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1923      +/-   ##
==========================================
- Coverage   87.12%   87.10%   -0.02%     
==========================================
  Files         165      165              
  Lines        4596     4596              
==========================================
- Hits         4004     4003       -1     
- Misses        592      593       +1     

Impacted Files	Coverage Δ
...i/include/opentelemetry/trace/propagation/jaeger.h	97.68% <ø> (ø)
sdk/src/trace/batch_span_processor.cc	90.70% <0.00%> (-0.77%)	⬇️

[lalitb]

Thanks, a very well thought-out and documented process. This will indeed smoothen the deprecation process. Have few nit comments :)

[esigo]

LGTM
Thanks for the PR :)

[marcalff]

Done with the last edits, now ready for formal review and merge.

[lalitb]

LGTM.
Nit: doc update for Jaeger deprecation -

• https://github.com/open-telemetry/opentelemetry-cpp/blob/main/exporters/jaeger/README.md
• https://github.com/open-telemetry/opentelemetry.io/blob/main/content/en/docs/instrumentation/cpp/exporters.md#jaeger

[marcalff]

LGTM. Nit: doc update for Jaeger deprecation -

* https://github.com/open-telemetry/opentelemetry-cpp/blob/main/exporters/jaeger/README.md

Thanks, fixed.

* https://github.com/open-telemetry/opentelemetry.io/blob/main/content/en/docs/instrumentation/cpp/exporters.md#jaeger

Actually, this doc needs no changes.

The Jaeger Exporter is deprecated, not Jaeger itself.

This documentation is about setting up Jaeger, and sending traces using OTLP HTTP, which is not affected.

[lalitb]

This documentation is about setting up Jaeger, and sending traces using OTLP HTTP, which is not affected.

Yes, didn't realize it is using OTLP exporter to send the traces.