tweak list_products to consider load_hints

[Ariana-B]

Reason for this pull request

list_products would always get crs and resolution from grid_spec even if default_crs or default_resolution is not None or if crs and resolution were defined via load_hints.

Proposed changes

• Return default values if present

• Don't ignore load_hints if not

  • [x] Closes #1531
  • [x] Tests added / passed
  • [x] Fully documented, including docs/about/whats_new.rst for all changes

---

📚 Documentation preview 📚: https://datacube-core--1535.org.readthedocs.build/en/1535/

[codecov[bot]]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (47f0aca) 91.79% compared to head (f547d7b) 91.77%.

Files	Patch %	Lines
datacube/api/core.py	57.14%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #1535 +/- ## =========================================== - Coverage 91.79% 91.77% -0.02% =========================================== Files 132 132 Lines 14624 14631 +7 =========================================== + Hits 13424 13428 +4 - Misses 1200 1203 +3 ```

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