FEAT: Add `fieldset.describe()` #2895

Job	Run time
should run ci	8s
GHA Security Analysis using Zizmor	12s
cache-pixi-lock	2s
Flaky unit tests: ${{ matrix.os }} \| pixi run -e ${{ matrix.pixi-environment }} tests-flaky	1s
Unit tests: ${{ matrix.os }} \| pixi run -e ${{ matrix.pixi-environment }} tests	1s
Validation tests \| pixi run tests-validation	1s
TypeChecking: pixi run typing	1s
Integration: ${{ matrix.os }} \| pixi run -e ${{ matrix.pixi-environment }} tests-notebooks	1s
build-and-upload-nightly-parcels	1s
merge-test-artifacts	1s
	29s

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