Add Delta Data Skipping on Staging Area

[osopardo1]

Description

Fixes #235

Type of change

It is an enhancement, it does not affect the current writing algorithm/format.

Checklist:

Here is the list of things you should do before submitting this pull request:

• New feature / bug fix has been committed following the Contribution guide.
• Add comments to the code (make it easier for the community!).
• Add tests.
• Your branch is updated to the main-1.0.0 branch (dependent changes have been merged).

How Has This Been Tested? (Optional)

Added test to OTreeIndexTest to check if staging files are filtered properly.

[codecov]

Codecov Report

Attention: 12 lines in your changes are missing coverage. Please review.

Comparison is base (2d39821) 90.86% compared to head (681518e) 91.04%.
Report is 30 commits behind head on main-1.0.0.

Files	Patch %	Lines
...core/transform/StringHistogramTransformation.scala	76.47%	8 Missing ⚠️
...cala/io/qbeast/spark/index/OTreeDataAnalyzer.scala	96.22%	2 Missing ⚠️
...e/src/main/scala/io/qbeast/core/model/CubeId.scala	94.73%	1 Missing ⚠️
...st/core/transform/StringHistogramTransformer.scala	88.88%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##           main-1.0.0     #239      +/-   ##
==============================================
+ Coverage       90.86%   91.04%   +0.17%     
==============================================
  Files              93       93              
  Lines            2386     2445      +59     
  Branches          178      169       -9     
==============================================
+ Hits             2168     2226      +58     
- Misses            218      219       +1     

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