METK-144 Replace & Remove GribHandle

[pgeier]

Description

This PR removes the usage of metkit/GribHandle everywhere possible in favor of new CodesHandle.
Fully removal will change once subsequent PRs using old CodesHandle have been merged.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 38.51351% with 91 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.01%. Comparing base (15a0584) to head (c25e744).

Files with missing lines	Patch %	Lines
src/metkit/codes/CodesDataContent.cc	25.00%	42 Missing ⚠️
src/metkit/pointdb/PointIndex.cc	0.00%	16 Missing ⚠️
src/metkit/pointdb/GribFieldInfo.cc	0.00%	12 Missing ⚠️
src/metkit/codes/api/CodesAPI.cc	76.66%	7 Missing ⚠️
src/metkit/codes/GribHandle.cc	0.00%	6 Missing ⚠️
src/metkit/pointdb/GribHandleDataSource.cc	0.00%	5 Missing ⚠️
src/metkit/codes/BufrContent.cc	33.33%	2 Missing ⚠️
src/metkit/codes/BUFRDecoder.cc	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #153      +/-   ##
===========================================
- Coverage    54.31%   54.01%   -0.31%     
===========================================
  Files          298      297       -1     
  Lines        11514    11490      -24     
  Branches      1021     1022       +1     
===========================================
- Hits          6254     6206      -48     
- Misses        5260     5284      +24     

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