Document deprecation process

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Is your feature request related to a problem? Please describe. Process not documented

Describe the solution you'd like Document process and reference.

• Issue requesting deprecation gets reviewed by CCB, accepted/assigned or rejected
  • evaluate requirements/documentation/operational impacts
• Pull request(s) wraps deprecated elements in *_OMIT_DEPRECATED ifndef and removes any internal dependencies
  • Default sample configuration does not remove this code
  • make OMIT_DEPRECATED=true prep will compile without it to check code for compliance
  • ideally any deprecated elements address dependency fix (use new element, no longer supported, etc)
  • elements can be deprecated in any build/release
  • CI tests with and without deprecated elements removed to ensure no internal dependencies
• Issue requesting removal of deprecated code
• Pull request removes deprecated elements
  • typically done end of cycle prior to a major release

Describe alternatives you've considered Wing it.

Additional context None

Requester Info Jacob Hageman - NASA/GSFC

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Suggest adding to a cfe/docs/src/*.dox file and referencing such that it gets into the autogenerated documentation.