runtime: refactor fpunwindExpand to use provided buffer
fpunwindExpand currently allocates a new slice to hold the expanded call
stack. In each place it's used, the resulting slice won't be needed
immediately afterward, so the allocation is wasteful. Refactor
fpunwindExpand to instead expand the call stack into a provided buffer.
Change-Id: I05b26c191a8f76404c21ccbe3bd422325540425b
Reviewed-on: https://go-review.googlesource.com/c/go/+/543715 Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Michael Knyszek <mknyszek@google.com> Reviewed-by: Michael Pratt <mpratt@google.com>