runtime: avoid large object stack copy in traceStackTable.dump
Following up on the previous CL, this CL removes a unnecessary stack
copy of a large object in a range loop. This drops another 64 KiB from
(*traceStackTable).dump's stack frame so it is now roughly 80 bytes
depending on architecture, which will easily fit on the system stack.
For #53979.
Change-Id: I16f642f6f1982d0ed0a62371bf2e19379e5870eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/422955
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Austin Clements <austin@google.com>