[Assets] Implement `pallet-assets-holder` #2865

Job	Run time
preflight / preflight	43s
check-runtime-assets	2m 29s
check-runtime-bridge-hubs	2m 14s
check-runtime-starters	0s
check-runtime-collectives	0s
check-runtime-coretime	0s
check-runtime-testing	0s
check-runtime-contracts	0s
All check-runtime-* tests passed	1s
	5m 27s

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