dashboard/app: show manager coverage #14939

Job	Run time
build	10m 45s
aux	4m 47s
dashboard	3m 27s
arch (presubmit_arch_linux)	10m 42s
arch (presubmit_arch_freebsd)	6m 33s
arch (presubmit_arch_netbsd)	4m 24s
gvisor	4m 23s
arch (presubmit_arch_openbsd)	4m 25s
old	6m 30s
arch (presubmit_arch_darwin)	4m 28s
arch (presubmit_arch_windows)	3m 22s
race	9m 4s
arch (presubmit_arch_executor)	3m 11s
race_dashboard	4m 20s
	1h 20m 21s

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