[Dexter][NFC] Add Debugger Controller To Dexter

  Add DebuggerControllerBase and DefaultController to Dexter
  implements a new architecture that supports new and novel ways of running
  a debugger under dexter.
  Current implementation adds the original default behaviour via the new
  architecture via the DefaultController, this should have NFC.

Reviewers: Orlando

Differential Revision: https://reviews.llvm.org/D76926