Cleanup unit tests: remove checks for imas-core

[prasad-sawantdesai]

Cleanup: Remove IMAS availability checks from test fixtures #91

• Removed has_imas and requires_imas fixtures from conftest.py since imas-core is now a mandatory dependency
• Updated all test functions and fixtures that used requires_imas to remove the parameter
• Simplified exception handling in conftest.py by removing defensive fallback code for ImasCoreBackendException since imas-core is always available

[maarten-ic]

CI has >100 failures and errors, can you have a look what's wrong and update the PR accordingly?

[prasad-sawantdesai]

CI has >100 failures and errors, can you have a look what's wrong and update the PR accordingly?

Yes, testing with MDSplus is skipped as imas_core Python package does not support the MDSplus backend.
https://github.com/iterorganization/IMAS-Python/pull/92/changes#diff-9d071ff1a106f23893c1e501b2bf7a51f40e33034917e60137e6655a2567b86e

[maarten-ic]

Looks good! I also checked the remainder of conftest and there's some more pieces that can probably be removed. Could you have a look at those as well?

[maarten-ic]

Great, nice cleanup of the code! :)