Migrate `pallet-indices` to umbrella crate #9033

Job	Run time
preflight / preflight	47s
preflight / ci-versions	1m 4s
test-frame-ui	26m 47s
cargo-check-benches (master)	20m 44s
test-full-crypto-feature	2m 30s
cargo-check-benches (current)	23m 33s
test-node-metrics	11m 41s
cargo-check-all-crate-macos	11m 34s
cargo-check-each-crate (1)	21m 18s
cargo-check-each-crate (2)	18m 35s
cargo-check-each-crate (3)	7m 50s
cargo-check-each-crate (4)	18m 31s
cargo-check-each-crate (5)	27m 12s
cargo-check-each-crate (6)	13m 8s
cargo-check-each-crate (7)	29m 33s
test-frame-examples-compile-to-wasm	2m 58s
test-deterministic-wasm	7m 36s
check-tracing	2m 17s
check-metadata-hash	6m 39s
node-bench-regression-guard	12s
All test misc tests passed	1s
	4h 14m 30s

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