mem-ruby: Move CacheMemory stats used in SLICC to a Stats group

mem-ruby: Move CacheMemory stats used in SLICC to a Stats group

This change moves some stats that are used in SLICC to a
separate Stats::Group.

In order to use stats in SLICC, new functions are added in
CacheMemory:
        - profileDemandHit()
        - profileDemandMiss()

The functions increase the corresponding stat by 1.

Change-Id: I52b6fefdf6579a49f626f2fca400641f90800017
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/37815
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Tiago Mück <tiago.muck@arm.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>