mem-cache: Create a tagged entry class

mem-cache: Create a tagged entry class

The TaggedEntry class inherits from the ReplaceableEntry
class. Its purpose is to define a replaceable entry with
tagging attributes.

It has been created as a separate class because both the
replacement policies and the AbstractCacheEntry use
ReplaceableEntry, and do not need the tagging information
to perform their operations.

Change-Id: I24e87c865fc21c79dea7e488507a8cafc5223b39
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/35698
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>