arch,sim: Handle KVM SE page faults with workload events.

arch,sim: Handle KVM SE page faults with workload events.

The event in KVM x86 SE mode plays double duty, triggering a system call
or a page fault depending on where it's called from (the system call
handler vs page fault handler).

This means we can eliminate the page fault gem5 op and the
pseudo_inst.hh switching header file.

This change touches a lot of things, but there wasn't really a good
place to split it up which still made sense and was consistent and
functional.

Change-Id: Ic414829917bcbd421893aa6c89d78273e4926b78
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/34165
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Alexandru Duțu <alexandru.dutu@amd.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>