feat(criterion): make `Bencher` implement `Send + Sync` #756

Job	Run time
lint	53s
lint-windows	3m 18s
tests	13m 36s
compat-integration-test-walltime (codspeed-divan-compat)	1m 48s
msrv-check	51s
compat-integration-test-instrumentation (-p codspeed-divan-compat)	1m 28s
compat-integration-test-walltime (codspeed-divan-compat-examples)	3m 12s
compat-integration-test-instrumentation (--features async_futures -p codspeed-criterion-compat)	2m 48s
compat-integration-test-walltime (codspeed-criterion-compat)	9m 38s
compat-integration-test-instrumentation (-p codspeed-bencher-compat)	1m 9s
compat-integration-test-instrumentation (-p codspeed-divan-compat-examples)	2m 1s
compat-integration-test-instrumentation (-p codspeed)	2m 25s
check	2s
	43m 9s

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