Fix/grid consistency check

[pawel-wolff]

Description

This PR fixes the issue #1000.

The proposed solution enforces the grid consistency check across fields from which xr_engine is trying to build an xarray.Dataset object. The grid check is based on Field.geography.unique_grid_id().

Additionally, the following related changes have been made:

• If the grid consistency fails, a diagnostic message is passed along with the exception.
• src/earthkit/data/core/field.py:Field.from_components(): if no geography is given but shape_hint is known (from values or data), an EmptryGeography(shape_hint) object is attached to a constructed field rather than a bare EmptyGeography(). This allows both:
  • keeping the existing logic for grid uniqueness (where bare EmptyGeography() instances are all distinct), see IndexFieldListBase._has_shared_geography.
  • a list-of-dicts with values and with no geography to be successfully converted into an xarray.Dataset; see, for example, this test

    earthkit-data/tests/xr_engine/test_xr_engine_lod.py

    Line 172 in 84aa271

    def test_xr_engine_lod_nongeo(allow_holes, lazy_load, xr_lod_nongeo):

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 95.45455% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.54%. Comparing base (84aa271) to head (0ad8fb2).
⚠️ Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
tests/netcdf/test_netcdf_output.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1003      +/-   ##
===========================================
+ Coverage    81.51%   81.54%   +0.02%     
===========================================
  Files          236      236              
  Lines        15472    15493      +21     
  Branches       756      756              
===========================================
+ Hits         12612    12633      +21     
  Misses        2634     2634              
  Partials       226      226              

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