cpu,sim: Delegate PCEvent scheduling from Systems to ThreadContexts.

The System keeps track of what events are live so new ThreadContexts
can have the same set of events as the other ThreadContexts.

Change-Id: Id22bfa0af7592a43d97be1564ca067b08ac1de7c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22106
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
6 files changed