Use actual runtime instead of a single thread #1084

Job	Run time
Measure coverage	3m 30s
Basic Checks	5m 38s
miri	3m 13s
Additional Builds and Concurrency Tests	14m 39s
Release builds and tests	9m 17s
sanitize (address)	18m 31s
Slow tests	53s
sanitize (address, multi-threading)	20m 10s
sanitize (leak)	3m 13s
sanitize (leak, multi-threading)	4m 3s
	1h 23m 7s

Provide feedback