Migrate `from_copernicusmarine` to use `from_sgrid_conventions` #1998

Job	Run time
cache-pixi-lock / Generate output	12s
Unit tests: ubuntu \| pixi run -e test-py313 tests	3m 47s
Unit tests: ubuntu \| pixi run -e test-minimum tests	3m 31s
Unit tests: windows \| pixi run -e test tests	6m 37s
Unit tests: ubuntu \| pixi run -e test tests	2m 42s
Unit tests: ubuntu \| pixi run -e test-py311 tests	3m 33s
Integration: ${{ matrix.os }} \| pixi run -e ${{ matrix.pixi-environment }} tests-notebooks	0s
TypeChecking: pixi run typing	0s
merge-test-artifacts	0s
	20m 22s

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