Fix typing

[sco1]

Once Mypy is updated to support pattern matching, need to go through and make sure our typing is correct.

[sco1]

Support for this is now on mypy's master branch, so the poking around on this can commence.

mypy's next release (0.940) is expected sometime in February.

[sco1]

Most of the low hanging fruit should now be taken care of, leaving a couple major things to work on:

• LoxArray
  • While everything works at runtime, inheriting from LoxInstance is causing some non-trivial (I think) typing issues, mostly around re-using fields to hold LoxArray's internal data as a deque vs. LoxInstance's dict. I'm not sure if this needs an entire refactor or if we can do something like putting the deque into a "__data__" field instead.
• Interpreter
  • The type narrowing, particulary with visitors like visit_Binary is a bit of a mess. Will have to take a look and see what we can do to narrow our left/right expressions down from Any to make the typing robust.
• AstPrinter
  • WIP, can handle at the same time as Update ast prettifier to handle the updated grammar #13