Multiprocessing: Ability to parallelize the pipeline steps

[coderustic]

As of now UnitTestGenerator has a sequence of steps finding the line number where to test headers and where to insert tests, building prompt, etc. It would be good to parallelize these steps.

[coderustic]

For this issue, we can just have the Generator be parallelized but continue to have validator to be sequentially iterating thru each test. But eventually we need to think how to parallelize test validations since it involves coverage step. Finding the flakiness can still be parallelized but then we need to figure out a way to isolate single test coverage check.