Refactor TxSet validation logic. (#4627) #6641

Job	Run time
cargo-deny (advisories)	56s
cargo-deny (bans licenses sources)	52s
fmt	19s
rust-check-git-rev-deps	18s
build (gcc, current)	1h 22m 4s
build (gcc, current, --check-test-tx-meta)	1h 2m 16s
build (gcc, next)	1h 26m 20s
build (gcc, next, --check-test-tx-meta)	1h 8m 7s
build (clang, current)	1h 1m 48s
build (clang, current, --check-test-tx-meta)	56m 38s
build (clang, next)	1h 5m 7s
build (clang, next, --check-test-tx-meta)	57m 47s
complete	1s
	9h 2m 33s

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