Revert "runtime: push down systemstack requirement for tracer where possible"

Revert "runtime: push down systemstack requirement for tracer where possible"

This reverts CL 572095.

Reason for revert: Broke longtest builders.

Change-Id: Iac3a8159d3afb4156a49c7d6819cdd15fe9d4bbb
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest
Reviewed-on: https://go-review.googlesource.com/c/go/+/577376
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>