runtime: fix list test memory management for mayMoreStack
The NIH tests simply failed to allocate the nodes outside the heap at
all. The Manual tests failed to keep the nodes alive, allowing the GC to
collect them.
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest
Change-Id: I6a6a636c434bb703d6888383d32dbf95fb0a15ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/719962
TryBot-Bypass: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com>