Use validator-adjusted active work for seq_join #5597

Job	Run time
miri	3m 4s
Additional Builds and Concurrency Tests	14m 33s
Measure coverage	27m 54s
Basic Checks	20m 15s
Release builds and tests	8m 22s
sanitize (address)	17m 36s
Slow tests	17m 13s
sanitize (address, multi-threading)	19m 36s
sanitize (leak)	7m 51s
sanitize (leak, multi-threading)	8m 27s
	2h 24m 51s

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