runtime: use FuncInfo SPWRITE flag to identify untraceable profile samples

The old code was very clever about predicting whether a traceback was safe.
That cleverness has not aged well. In particular, the setsSP function is missing
a bunch of functions that write to SP and will confuse traceback.
And one such function - jmpdefer - was handled as a special case in
gentraceback instead of simply listing it in setsSP.

Throw away all the clever prediction about whether traceback will crash.
Instead, make traceback NOT crash, by checking whether the function
being walked writes to SP.

This CL is part of a stack adding windows/arm64
support (#36439), intended to land in the Go 1.17 cycle.
This CL is, however, not windows/arm64-specific.
It is cleanup meant to make the port (and future ports) easier.

Change-Id: I3d55fe257a22745e4919ac4dc9a9378c984ba0da
Reviewed-on: https://go-review.googlesource.com/c/go/+/288801


Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>