mem-cache: Implement a multi compressor

mem-cache: Implement a multi compressor

Implement a compressor that contains multiple sub-compressors and
choses the one that provides the best compression results for each
compression.

Change-Id: I758cf67c84bd85edbea16b2a07b2068b00454461
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21158
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>