cmd/go/internal/work: add telemetry counters for build cache hits/misses
The following counters are added in this cl
go/buildcache/hit
go/buildcache/miss
go/buildcache/stdlibrecompiled (incremented at most once per
invocation)
Change-Id: Ia78e136feac8226cb35e554503b672343cc30262
Reviewed-on: https://go-review.googlesource.com/c/go/+/587577
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Robert Findley <rfindley@google.com> Reviewed-by: Sam Thanawalla <samthanawalla@google.com>