Refactor indices pallet to use fungible traits #36213

Job	Run time
isdraft / isdraft	3s
preflight / preflight	48s
preflight / ci-versions	1m 0s
check-revive-stable-uapi-polkavm	1m 49s
build-runtimes-polkavm	9m 56s
build-subkey	3m 44s
All build misc jobs passed	4s
	17m 24s

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