Fix bug in _ensure_increasing_x

[konstntokas]

• Fixed a bug in xcube_resampling.rectify_dataset that occurred when processing
  datasets with decreasing x-coordinates.
• Boolean (bool) data arrays now default to nearest-neighbor interpolation.
  For spatial aggregation, values are centered, and 0 is used as the default fill
  value—matching the behavior of integer arrays to ensure consistent and valid results.

Checklist:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/
• Changes documented in CHANGES.md
• CI checks pass
• Test coverage remains or increases (target 100%)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.65%. Comparing base (d900146) to head (94a06e7).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #27   +/-   ##
=======================================
  Coverage   98.65%   98.65%           
=======================================
  Files          20       20           
  Lines        2006     2009    +3     
=======================================
+ Hits         1979     1982    +3     
  Misses         27       27           

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