Migrate `pallet-assets-freezer` to umbrella crate #9124

Job	Run time
preflight / preflight	36s
preflight / ci-versions	58s
cargo-check-all-crate-macos	11m 15s
cargo-check-each-crate (1)	23m 15s
cargo-check-benches (master)	22m 7s
cargo-check-each-crate (2)	20m 28s
cargo-check-benches (current)	23m 30s
cargo-check-each-crate (3)	9m 29s
test-frame-ui	46m 36s
cargo-check-each-crate (4)	20m 52s
cargo-check-each-crate (5)	29m 15s
test-full-crypto-feature	2m 33s
cargo-check-each-crate (6)	14m 50s
test-node-metrics	10m 39s
cargo-check-each-crate (7)	28m 59s
test-frame-examples-compile-to-wasm	2m 53s
test-deterministic-wasm	7m 54s
check-tracing	2m 13s
check-metadata-hash	7m 0s
node-bench-regression-guard	16s
All test misc tests passed	1s
	4h 45m 39s

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