Collect coverage information at end of tests.

https://www.veripool.org/projects/verilator/wiki/Manual-verilator

1. Pass --coverage option to verilator in makefile
2. Modify c++ test harness to VerilatedCov::write into an output file. There will be one file per test, which should be collected somewhere (this probably needs to be done by test_harness.py)
3. Run verilator_coverage executable,

For instance, if a user tries to write jalr x0 0(x1) the tooltip should also state that jalr has the format
jalr [rd] [rs] [imm].

We should probably have a general cleanup of configureLink when links are not allowed to be nullptr. This causes errors to be seg faults, instead of simple errors messages like "you forgot to add the expected link X"

Describe the bug
Command and instruction are used interchangeably in the taint code but they are two different things.

To Reproduce
N/A

Expected behavior
Sunflower commands should be referred to as commands and RISC-V instructions should be referred to as instructions. Someone should go through and ensure that command only refers to sunflower commands and instruction only refe