Add a command line option to list available stat formats and their documentation. Change-Id: I7f5f2272d9b0176639f59f2efedb9cab2f7da5b9 Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19670 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Tested-by: kokoro <noreply+kokoro@google.com>