handle optional dependencies in tests

[colonesej]

This pull request improves test robustness and reliability by adding conditional skips to tests that depend on optional modules such as geopandas and pyodc. It introduces new flags in the testing utilities to check for the presence of these dependencies and updates relevant tests to skip execution gracefully if the required modules are missing, preventing unnecessary test failures.

Test robustness and conditional skipping:

• Added NO_ODC and NO_GEOPANDAS flags in earthkit.data.utils.testing to check for the presence of pyodc and geopandas modules, respectively.
• Updated ODB-related tests to skip at the module level if pyodc is not installed, using NO_ODC and pytest.skip. [1] [2] [3] [4] [5]
• Updated GeoPandas-related tests to skip if geopandas is not installed, using NO_GEOPANDAS and pytest.mark.skipif or pytest.skip. [1] [2] [3] [4] [5] [6] [7]

These changes ensure that tests requiring optional dependencies do not fail unnecessarily, improving the reliability of the test suite across different environments.

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 69.69697% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.41%. Comparing base (ffe0e1f) to head (3bdda87).

Files with missing lines	Patch %	Lines
tests/high_level_object/test_hl_odb_core.py	50.00%	1 Missing and 1 partial ⚠️
tests/odb/test_odb_pandas.py	50.00%	1 Missing and 1 partial ⚠️
tests/odb/test_odb_url.py	50.00%	1 Missing and 1 partial ⚠️
tests/readers/test_geojson_reader.py	33.33%	1 Missing and 1 partial ⚠️
tests/readers/test_shapefile_reader.py	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1038      +/-   ##
===========================================
- Coverage    82.44%   82.41%   -0.04%     
===========================================
  Files          237      237              
  Lines        16698    16722      +24     
  Branches       808      813       +5     
===========================================
+ Hits         13767    13781      +14     
- Misses        2694     2699       +5     
- Partials       237      242       +5     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.