This change creates the runtime/metrics package and adds the initial
interface as laid out in the design document.
For #37112.
Change-Id: I202dcee08ab008dd63bf96f7a4162f5b5f813637
Reviewed-on: https://go-review.googlesource.com/c/go/+/247040
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Michael Knyszek <mknyszek@google.com> Reviewed-by: Michael Pratt <mpratt@google.com>