runtime: factor out GC pause time CPU stats update
Currently this is done manually in two places. Replace these manual
updates with a method that also forces the caller to be mindful that the
number will be multiplied (and that it needs to be). This will make
follow-up changes simpler too.
Change-Id: I81ea844b47a40ff3470d23214b4b2fb5b71a4abe
Reviewed-on: https://go-review.googlesource.com/c/go/+/570255
Auto-Submit: Michael Knyszek <mknyszek@google.com> Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>