Tests: Add Tests to contains Filter Operator on PostgreSQL Backend

[rabbull]

This PR adds tests to validate the behavior of the contains operator when applied to JSON objects and arrays in the PostgreSQL backend. The tests cover a variety of scenarios, including type matching, negations, and edge cases such as empty arrays or objects. This is a test-only PR, and no features or functionality in aiida-core have been modified.

Some corner case behaviors appear unintuitive and will be documented in a separate issue for further investigation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.90%. Comparing base (ef60b66) to head (2113fa9).
Report is 140 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6617      +/-   ##
==========================================
+ Coverage   77.51%   77.90%   +0.40%     
==========================================
  Files         560      567       +7     
  Lines       41444    42147     +703     
==========================================
+ Hits        32120    32831     +711     
+ Misses       9324     9316       -8     

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[GeigerJ2]

Great work, @rabbull, thanks for adding those extensive tests. I'd say we get this merged, and then figure out how we can resolve the unexpected behaviors.

I'd use the first paragraph of this PR description as the commit message for the squashed commit. Is that fine for you, or would you like something else? If so, please comment the text here. Thanks!

[rabbull]

I'd use the first paragraph of this PR description as the commit message for the squashed commit.

Sure, this LGTM. :)

[GeigerJ2]

Very nice work, thanks a lot for extending the tests so thoroughly, @rabbull! Some minor proposals to extend them further.