[WIP] BYOC Support for BlackParrot RV64GC

[dpetrisko]

This PR adds support for BlackParrot simulation to OpenPiton via the BYOC framework. OpenPiton+BlackParrot on FPGA is currently beta (read: broken =)). WIP until the FPGA version works or we find out it's too much trouble.

There is a necessary fix to the L2 cache, which replicates the data of subword requests, as required by P-Mesh. This should be compatible with existing implementations which mux the word from the correct byte offset. It just allows implementations to be lazy and use whichever is more convenient. I can separate this out to a second PR if helpful.

Depends on:

• Fix bytewidth parameter in OpenPiton bootrom AXI-lite bridge openhwgroup/cva6#1264
• Adding P-Mesh engines and tile black-parrot-hdk/black-parrot-subsystems#29