Parallelize decryption of reports #5619

Job	Run time
Basic Checks	10m 32s
miri	3m 2s
Additional Builds and Concurrency Tests	15m 36s
Measure coverage	9m 16s
Release builds and tests	11m 57s
Slow tests	21m 8s
sanitize (address)	18m 0s
sanitize (address, multi-threading)	19m 25s
sanitize (leak)	7m 53s
sanitize (leak, multi-threading)	8m 37s
	2h 5m 26s

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