Alias `FillValueMetadata` and `Metadata` with deprecations #558

Job	Run time
build_and_test_macos (macos-13)	1m 47s
clippy	41s
build_and_test_windows	4m 32s
build (stable, --features "")	37s
build_and_test_macos (macos-latest)	1m 19s
build (stable, --all-features)	1m 19s
fmt	19s
codecov	3m 52s
build (stable, --no-default-features)	47s
build (1.76, --features "")	45s
build (1.76, --all-features)	1m 50s
semver	58s
minimal-versions	2m 6s
test	2m 9s
build (1.76, --no-default-features)	48s
build (beta, --features "")	40s
build (beta, --all-features)	1m 46s
build (beta, --no-default-features)	50s
build (nightly, --features "")	36s
build (nightly, --all-features)	1m 18s
build (nightly, --no-default-features)	49s
	29m 48s

Provide feedback