Migrate `pallet-assets-freezer` to umbrella crate #9496

Job	Run time
preflight / preflight	46s
preflight / ci-versions	1m 13s
cargo-check-benches (master)	20m 51s
cargo-check-benches (current)	25m 44s
cargo-check-all-crate-macos	11m 37s
test-frame-ui	47m 52s
cargo-check-each-crate (1)	29m 59s
test-node-metrics	12m 42s
test-full-crypto-feature	2m 33s
cargo-check-each-crate (2)	31m 32s
cargo-check-each-crate (3)	10m 33s
cargo-check-each-crate (4)	30m 21s
cargo-check-each-crate (5)	49m 47s
cargo-check-each-crate (6)	19m 23s
cargo-check-each-crate (7)	52m 6s
test-frame-examples-compile-to-wasm	3m 0s
test-deterministic-wasm	7m 44s
check-tracing	2m 22s
check-metadata-hash	6m 56s
node-bench-regression-guard	11s
All test misc tests passed	1s
	6h 7m 13s

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