cmd/internal: separate counter package from telemetry package

cmd/internal: separate counter package from telemetry package

Move the code that opens and increments counters out of the
cmd/internal/telemetry package into cmd/internal/telemetry/counter. The
telemetry package has dependencies on the upload code, which we do not
want to pull into the rest of the go toolchain.

For #68109

Change-Id: I463c106819b169177a783de4a7d93377e81f4e3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/593976
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>