start to reorganise the NMI fault implementation

Created by: eroom1966

@strichmo @MikeOpenHWGroup Mike, Steve, I am starting to re-structure the model to handle our discussions earlier this week The only structural change you should be aware of (part of this commit) is that the Load,Store,Fetch Fault signals have moved into the RVVI_io interface I have changed the reference to these signals accordingly in lib/uvm_agents/uvma_rvvi_ovpsim/seq/uvma_rvvi_ovpsim_obi_seq.sv

Thx Lee