Make Preparations for GLAMOD data release 9.0

[ludwiglierhammer]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes Preparations for GLAMOD data release 9.0 #445
• (If applicable) Documentation has been added / updated (for bug fixes / features).
• (If applicable) Tests have been added.
• CHANGELOG.rst has been updated (with summary of main changes).
  • Link to issue (:issue:number) and pull request (:pull:number) has been added.

What kind of change does this PR introduce?

This PR updates cdm_reader_mapper for the upcoming GLAMOD data release 9.0.

1. When reading a ParquetStreamReader, the columns will be restored from string literals.
2. ...

Does this PR introduce a breaking change?

See above 1.

Other information:

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.07%. Comparing base (401259e) to head (ce2d2ed).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #447      +/-   ##
==========================================
+ Coverage   97.05%   97.07%   +0.02%     
==========================================
  Files          78       78              
  Lines        3496     3520      +24     
==========================================
+ Hits         3393     3417      +24     
  Misses        103      103              

Flag	Coverage Δ
unittests	97.07% <100.00%> (+0.02%)	⬆️

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