dev: Enable Terminal output's dump to stdout

dev: Enable Terminal output's dump to stdout

While the default option is to dump the Terminal content in a file (e.g.
m5out/system.terminal), with this patch it will be possible to choose to
dump it to standard output.

Change-Id: If51c2fd671fa3eb0867a855b5f7d3b0df9cad025
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20639
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>