Add several benchmarks for pprof labels to analyze the impact of
follow-up CLs.
Change-Id: Ifae39cfe83ec93858fce9e3af6c1be024ba76736
Reviewed-on: https://go-review.googlesource.com/c/go/+/574515
Auto-Submit: Ian Lance Taylor <iant@golang.org> Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Michael Pratt <mpratt@google.com>