This change introduces the trivial traceEnabled function to help tighten
up the execution tracer's API in preparation for the execution trace
redesign GOEXPERIMENT.
A follow-up change will refactor the runtime to use it.
Change-Id: I19c8728e30aefe543b4a826d95446affa14897e3
Reviewed-on: https://go-review.googlesource.com/c/go/+/494180
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com> Reviewed-by: Michael Pratt <mpratt@google.com>