Update `_validate_against_pure_literal` to fail on Xarray objects (#2… #2318

Job	Run time
should run ci	7s
cache-pixi-lock	1m 32s
Unit tests: ubuntu \| pixi run -e test tests	2m 59s
Unit tests: ubuntu \| pixi run -e test-py313 tests	4m 33s
build-and-upload-nightly-parcels	2m 6s
Unit tests: ubuntu \| pixi run -e test-py311 tests	4m 7s
Unit tests: ubuntu \| pixi run -e test-minimum tests	4m 3s
Unit tests: windows \| pixi run -e test tests	7m 28s
Integration: ${{ matrix.os }} \| pixi run -e ${{ matrix.pixi-environment }} tests-notebooks	0s
TypeChecking: pixi run typing	0s
merge-test-artifacts	0s
	26m 55s

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