Descriptor-based frontend: proposed enhancements.

[thommythomaso]

• Evaluate whether to keep the testbench without the backend
• Maybe add the Linux driver from Gitlab here as a patch file (and remove the questionable hotqueueing)
• Move the bare-metal driver from the cva6-repo on Gitlab to here
• Maybe test more size/prefetching combinations to tease out more potential deadlocks and logic loops.
• Need to check if I messed something up with the linting rules
• More comments in the implementation would be nice