Mutation testing - Logger for missing/timeout/unviable tests

[ASuciuX]

logger which has the role of keeping track of all the functions that weren't tested before implementing this. Its final role is to be removed by having complete completion, but till that point, it makes it a lot easier to see which functions need extra tests and add them. On **merge**, it will run cargo mutants in the same way as the filter-pr and will modify the logged output with the information from the new generated output. (eg. fn A had missing tests before, now it has the tests. it will be removed from missed.txt and appended to caught.txt)