add codesearch tool #18306

Job	Run time
build	3m 8s
aux	4m 12s
dashboard	2m 4s
race_dashboard	3m 33s
arch (presubmit_arch_netbsd)	3m 50s
race	8m 58s
arch (presubmit_arch_freebsd)	6m 21s
arch (presubmit_arch_darwin)	3m 49s
arch (presubmit_arch_openbsd)	3m 43s
arch (presubmit_arch_linux)	10m 39s
arch (presubmit_arch_executor)	3m 28s
gvisor	3m 50s
arch (presubmit_arch_windows)	3m 49s
old	7m 23s
	1h 8m 47s

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