Remove old scripts/files

Created by: jordancarlin

I started removing old scripts and files in PR #978. These are additional files that can likely be removed or need to be updated, but I'm not sure about all of them.

• sim/
  • bp-results - retained for now (possibly look for better solution later) per @rosethompson
    • Should this be here? Seems like references to a bunch of log files.
  • buildrootBugFinder.py
    • Not currently working. Update or remove?
  • bpred-sim.py
    • Not currently working. Update or remove?
  • xcelium
    • Not compatible with wsim, not tested regularly. Should this be removed?
  • FPBuild.txt
    • Move relevant parts to tests/fp/README.md and then remove
  • questa/fpga-wave.do - retained per @rosethompson
    • Is this used anywhere? Seems like it can be removed.
• tests/
  • custom (see #984)
    • Many of these are not run. Are they all still needed or should they be pruned down? Any that are retained should probably be part of regression.
• studies/
  • testgen
    • All of the scripts depend on imperas-riscv-tests, which is not in the repo anymore. Should these be removed?
• fpga/
  • generator/bootmem.txt
    • Is this still needed? Isn't the current version generated by the zsbl Makefile?
  • sim
    • Are these all still used?
• dvtestplan.md and docs/testplans/testplan.md are redundant and should be combined
• gitflow.txt
  • This should either be updated to align with the book (https vs ssh) or removed and just rely on the new user setup in the README and textbook