Merge testbench-imperas.sv into testbench.sv

Created by: rosethompson

Merges testbenches together and updates wally.do and wsim to support lockstep simulation with imperasDV. Also add single elf file regression to wsim, wally.do, and testbench.sv. The following are tested regression-wally

single elf wsim --elf single elf with lockstep wsim --elf --lockstep single elf, lockstep + GUI wsim --elf --lockstep --gui

buildroot wsim buildroot buildroot --lockstep wsim buildroot buildroot --lockstep --gui

I'll add the latest changes modified MISA so lockstep finds an error with buildroot at ~189K instructions. I want to merge this anyway.

I added another option --locksteplog (-b) which takes an option parameter that specifies when to turn on ImperasDV logging. There appears to be a bug with imperasDV not turning on the logger at the correct time. I'm not sure exactly what the issue is yet. wsim buildroot buildroot --lockstep -b 1000

For now, I've left the existing testbench-imperas.sv and wally-imperas.do and other files in the repo until we are happy with these changes. I suspect we are ok to merge this PR now and then make changes are we see fit.