cmd/compile: mark PanicBounds/Extend as calls

PanicBounds and PanicExtend are lowered to runtime calls (with a
non-Go ABI), but are not currently marked as calls. Since liveness
analysis only emits stack maps at calls in the runtime, this means
these panic call sites in the runtime won't get a stack map. These
almost immediately turn into throws in the runtime, but there's still
a chance they'll try to grow the stack first, which would lead to a
different panic.

To fix this, mark these operations as calls.

Outside the runtime, we currently emit stack maps for everything that
isn't an unsafe-point, so these panic calls get stack maps by default.
However, we're about to move to emitting stack maps only at call
sites, at which point this will start to matter outside the runtime as
well.

I confirmed that this has no effect on anything but PCDATA/FUNCDATA in
runtime and net/http.

For #36365.

Change-Id: Ic5bb463fd152cc320c815dc04cf62005261ae169
Reviewed-on: https://go-review.googlesource.com/c/go/+/230539


Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>