[FIX] Update CI, tests and deprecations

[elephaint]

Deprecates the old evaluation method in:

• [x] ~~Tests~~ Skipped because not all lossses have been transferred to utilsforecast yet.
• [x] ~~Experiments~~ Skipped because not all lossses have been transferred to utilsforecast yet.
• [x] Action files

Updates CI with probabilistic cases.

Updates readme to use uv instead of conda.

Includes Python 3.13 in CI.

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