GFE integration - post open-source

This is an enumeration of the tasks ported to post-open-source from #1002:

[ ] One liner to load a bitstream and a binary for easy testing (or should we introduce a mode into BESSPIN-Tool-Suite?).
[ ] One liner to program FPGA with a bitstream (flash/nonpersistent) (or should we introduce a mode into BESSPIN-Tool-Suite?).
[ ] Benchmarks (should be a separate "mode" of the BESSPIN-Tool-Suite)
[ ] openocd/gdb scripts for starting proper debug sessions
[ ] a bunch of tests to test/evaluate processors
[ ] linux build (nix just uses GFE scripts)
[ ] FreeBSD build (how is this handled in nix?)
[ ] emulation/simulation of the CPUs (spike,verilator)
[ ] Any more renaming/refactoring/removing or integration into BESSPIN-Tool-Suite?

GaloisInc / BESSPIN-Tool-Suite