sim: Add a mechanism for finding an compatible SE workload.
sim: Add a mechanism for finding an compatible SE workload.

This makes it possible to pick an SEWorkload generically at the config
level and not in C++ after the structure of the simulation has already
been set.

Change-Id: I7e52beb5a4d45aa43192e1ba4de6c5aab8b43d84
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33900
Reviewed-by: Andreas Sandberg <c9f5686ee5bd561c93f9de79681eee75bfa7f36e@arm.com>
Maintainer: Andreas Sandberg <c9f5686ee5bd561c93f9de79681eee75bfa7f36e@arm.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5