Fix Indexed value equality

[soininen]

The previous method failed e.g. when index type for Maps was datetime. numpy.array_equal() works on all arrays and data types.

Fixes spine-tools/Spine-Toolbox#2806

Checklist before merging

• [x] Documentation (also in Toolbox repo) is up-to-date
• [x] Release notes have been updated
• [x] Unit tests have been added/updated accordingly
• [x] Code has been formatted by black
• [ ] Unit tests pass

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 78.20%. Comparing base (bf01ac8) to head (beaedef).

Files	Patch %	Lines
spinedb_api/parameter_value.py	66.66%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #415 +/- ## ========================================== - Coverage 78.21% 78.20% -0.02% ========================================== Files 72 72 Lines 9517 9519 +2 Branches 2032 2034 +2 ========================================== Hits 7444 7444 - Misses 1737 1738 +1 - Partials 336 337 +1 ```

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