Refactor TxSet validation logic. #6620

Job	Run time
cargo-deny (advisories)	46s
rust-check-git-rev-deps	18s
fmt	25s
cargo-deny (bans licenses sources)	38s
build (gcc, current)	56m 34s
build (gcc, current, --check-test-tx-meta)	1h 2m 6s
build (gcc, next)	1h 1m 55s
build (gcc, next, --check-test-tx-meta)	1h 4m 17s
build (clang, current)	46m 32s
build (clang, current, --check-test-tx-meta)	43m 29s
build (clang, next)	51m 46s
build (clang, next, --check-test-tx-meta)	44m 42s
complete	1s
	7h 13m 29s

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