Nonmatching grid tests

[zhangyh0713]

Proposed changes

Issue: #1312
We created a new class to generate non-matching grids, which can handle cases with 0 to 2 orthogonal fractures. It returns a refined fracture set and a refined interface map. Its functionality is tested in test_fluid_mass_balance.py. The fluid mass problem, previously tested only on matching grids, is also tested with non-matching grids.

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• Minor change (e.g., dependency bumps, broken links).
• Bugfix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
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Checklist

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• The documentation is up-to-date.
• Static typing is included in the update.
• This PR does not duplicate existing functionality.
• The update is covered by the test suite (including tests added in the PR).
• If new skipped tests have been introduced in this PR, pytest was run with the --run-skipped flag.

[keileg]

Nice work. I added some comments, and suggest to delete most of the documentation that reflect the development, rather than the result.

Main request: This function will be much more useful (also outside tests) if the user can controll the refinement process in fractures and interfaces. Please consider how this can be controlled by using parameters.

[keileg]

We should also make sure the geometry setup is directly tested, not just through the inclusion in higher-order tests.

[IngridKJ]

Note to selves after randomly meeting @keileg in the hallway: Make a test for testing the geometry itself.

[keileg]

This look fairly good now. Let's try to do a final change in today's session: We see if we can move the actual mesh generation to mdg_library, and let the class NonMatchingSquareDomainOrthhhogonalFractures fetch from the library.