parse: Add function to fully format an error

tests: Always draw a task for ParseContext

parse: Add function to format a ParseContext for display

parse: Add function to format a ParseErrorException for display

tests: Document parse error data structures

tests: Fix draw_maybe ratio ...

I wrote this code while really tired and of course an off by one error
slipped in.

tests: Use a proper values for structural ParseContext tests

src: Check for None in all __eq__ methods ...

This lets us finally compare parse error exceptions and contexts of
different shapes.

main: Put executable name in usage

main: Add run_file function for REPL use ...

This should help using NewLang from micropython.

log: Rely on main for the getenv call ...

micropython on the Pi Pico for some reason doesn't support getenv, so
try and push this in to main where we can decide to use it.

main: Remove unused nowait_main function

port: Add micropython-compatible atexit wrapper

run: Use run.py to run src/main.py ...

This completely removes the weird logic for editing paths at the expense
of some more code.

i18n: Add mutation tests

i18n: Add new module containing a Message class ...

This Message class will be used to format localized text later.

tests: Move parser error tests to its own file

parse: Have parse run parse_file

parse: Actually add parser code for real this time I promise

parse: Add file parser

parse: Add directive parser

tests: Fix draw_wrong_statement_at drawing invalid values

tests: Note what we expect for test_parse_set_valid

env: Add dotest_dev command ...

This is mainly when doing development and writing tests. It shows more
detailed error logs for failing tests.

tests: Copy tokens in template_test_invalid ...

This makes debugging easier as our input data isn't consumed.

parse: Add conditional statement parser

parse: Add Set node parse code ...

I've taken a different approach this time with my tests by avoiding
decorated functions where I can and adding big upfront documentation
about how things work.

I've deprecated the old decorated functions and hopefully will remove
them during a refactor and cleanup.

env.ps1: Give up on proper error checking ...

PowerShell functions don't propagate errors so don't rely on it for
pipelines.

Bug: https://github.com/PowerShell/PowerShell/issues/12218

env.ps1: Print mutmut results on error on Windows

env: Print mutmut results on error on Linux