pallet-vesting: add try_state invariant checks #47856

Job	Run time
isdraft / isdraft	3s
preflight / preflight	56s
preflight / ci-versions	1m 10s
check-revive-stable-uapi-polkavm	26s
build-runtimes-polkavm	6m 41s
build-subkey	2m 33s
All build misc jobs passed	3s
	11m 52s

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