pkg/codesearch: support finding field reads/writes #19134

Job	Run time
build	5m 28s
dashboard	2m 28s
aux	4m 3s
old	6m 45s
arch (presubmit_arch_netbsd)	3m 56s
gvisor	4m 3s
race	9m 37s
arch (presubmit_arch_freebsd)	6m 41s
arch (presubmit_arch_darwin)	3m 50s
arch (presubmit_arch_windows)	3m 58s
arch (presubmit_arch_openbsd)	3m 26s
arch (presubmit_arch_linux)	10m 52s
arch (presubmit_arch_executor)	3m 18s
race_dashboard	3m 30s
	1h 11m 55s

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