feat(Mutator): Add mutator for GeneratedRegex

[Pentiva]

Adds the ability for Stryker to apply regex mutations to code using the GeneratedRegex attribute. Also switches usage in the library to use the regex source generator.

There are several things that I think aren't perfect about this implementation:

• All of the mutation is done in the orchestrator, instead of a mutator.
• The actual mutation does not match a manual mutation.
  • Therefore the JSON report has to be faked to make sense.
• The typical tests for the orchestrator was causing my IDE to lag very heavily, so VerifyTests was used.
• The SemanticModel has to be recomputed after a change, otherwise it is unusable in further mutations.
• Since GeneratedRegexOrchestrator needs to generate the mutants, it is now made available through the MutationContext.