[Feature] Estimator backends & common structure

[SBouchard01]

Caution

Delegated to #277 and #278 - Keeping this PR open to track changes to this branch until all is ported to #278

This PR updates the galaxy estimator and their backends to a common standard:

• Standardized backends
• Added tests for backend functionalities
• Updated tests syntax to match some ruff & ty rules (because the warnings were annoying)
• Reworked the base Estimator class with backend support & standard methods
  • Note that the backend attributes are now explicit to ensure consistency between backends !
• Reworked some estimators as examples
• Added unit tests for reworked estimators
• Updated example notebooks for updated estimators
• Tested consistency of reworked backend with previous results
• Added warnings to non-updated estimators
  • To allow the tests to pass I disabled type checking on purpose in the non-updated estimators. We expect the updates to remove the logging message and the # type: ignore on top of the file when ready.

Note

The backend unit tests are done with mocked imports, which means they don't check the output and the inputs are dummy values.
We will need to confirm the output are actually consistent and don't crash before merging !!

[SBouchard01]

Also I've moved _make_array (that I have taken from pyrecon and updated) to acm.utils.default, I was not sure where to put that helper function :)

[SBouchard01]

Closing, delegated to #277 and #278