Fix metaindx shift after metadata filter

[thorbjoernl]

Change Summary

The metadata index array was not correctly offset to match the new indices during metadata filter which caused lookup of metadata using UngriddedData.metadata to be broken after using UngriddedData.filter_by_meta()

Related issue number

closes #1354

Checklist

• Start with a draft-PR
• The PR title is a good summary of the changes
• PR is set to AeroTools and a tentative milestone
• Documentation reflects the changes where applicable
• Tests for the changes exist where applicable
• Tests pass locally
• Tests pass on CI
• At least 1 reviewer is selected
• Make PR ready to review

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.68%. Comparing base (d40203e) to head (b7ffcf9).
Report is 8 commits behind head on main-dev.

Additional details and impacted files

@@            Coverage Diff            @@
##           main-dev    #1355   +/-   ##
=========================================
  Coverage     78.68%   78.68%           
=========================================
  Files           136      136           
  Lines         20787    20788    +1     
=========================================
+ Hits          16357    16358    +1     
  Misses         4430     4430           

Flag	Coverage Δ
unittests	78.68% <100.00%> (+<0.01%)	⬆️

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