Clean up twisted.trial.runner

[exarkun]

Is your feature request related to a problem? Please describe.

twisted.trial.runner has some pretty cruft old stuff in it:

• It has an implicit interface with debuggers
• It manually implements resource allocation/cleanup for log files and the working directory
• TrialRunner has a dozen or more attributes manually defined and of poorly document types
• There are few type annotations
• There is loooong-since deprecated support for reporters with no done method
• The test suite involves monkey-patching implementation details to observe various side-effects
• The test suite involves monkey-patching implementation details to fix unexplained bugs which apparently no longer exist

All of this stuff gets in the way of trying to implement new features like #11671 . Let's start to clean it up.