Enables adding multiple VXS units to a design with varying supported instructions per VXS
Currently, this make each FU exclusive to a single VXS, which should cut down on unnecessary control logic, while also allowing us to achieve desired performance improvements (the design as instantiated creates one VXS that supports FMA-type instructions and another VXS that supports all other instructions)
Instantiating a single VXS that supports all instructions would correspond to what is currently in Saturn
Remaining TODOs:
[x] Comprehensive testing
[x] Improve the generator in the Backend/how different VXS's should be added
[x] Add support for instantiating multiple FUs of the same type (assuming the corresponding number of supporting VXS units are also instantiated)
Remaining TODOs: