mem-cache: Use AssociativeSet in Stride prefetcher

mem-cache: Use AssociativeSet in Stride prefetcher

Avoid replicating associative set functionality in Stride prefetcher's
pc tables.

The indexing policy used previously had some peculiarities, so both
the extractTag and extractSet have been made virtual so that previous
behavior could be kept.

Change-Id: I19a86cb3c4b40031fef427d5f7eed9d5c5673a44
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24603
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>