internal/trace: refactor Stack.Frames to return iter.Seq
The Frames function is almost an iter.Seq, except for its bool return
value.
Since none of the callers in the Go tree rely on the bool, we can remove
it. However, doing so might still obscure the intended usage as an iterator.
This refactor changes the API to return iter.Seq, making the intended
usage explicit. Refactoring the existing callers to take advantage of
the new interface will be done in a follow-up CL.
Change-Id: I03e4d6d762910e418cc37d59a6c519eb7f39b3b0
Reviewed-on: https://go-review.googlesource.com/c/go/+/608855
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com>