Outdated tests

Created by: jordancarlin

testbench.sv and tests.vh have many entries for tests that I believe are no longer used. Can all of these be removed or do any of them still exist for a particular reason?

• Many Imperas tests that reference the nonexistent imperas-riscv-tests directory
• wallycov64i seems to be a remnant from before cvw-arch-verif existed
• wally32d is listed in tests.vh but doesn't have an entry in testbench.sv, so it is not possible to run. It also seems like the instruction it is testing (fld for rv32) is likely already tested in the rv32 D extension riscv-arch-test tests, so it is probably not necessary.
• wally32i/wally64i aren't run in regression and seem redundant, especially now that we have cvw-arch-verif. At a minimum, the wally32i assembly files should be removed from the repo since they are generated by testgen.py. With cvw-arch-verif it seems like testgen.py can likely be entirely removed.