tests: tokenize: Run classification with random input

tokenize: Add classify_tokens to set token types

tests: tokenize: Rename draw_token to draw_token_random

tokenize: Add WHITESPACE TokenType ...

This will be used later.

tests: Use random token types for tokens

tokenize: Add type value for token type

src: tokenize: Rename symbol to token

tests: Generate random locations for symbols ...

This requires adding a new higher-order strategy to set the location of
a symbol.

tokenize: Add locate_symbols function to add symbol locations ...

This isn't the best soltuion yet, but it's a start.

tests: tokenize: Test symbol structure

tokenize: Always specify a location for symbols ...

This gets rid of the default symbol location. The 'default' used now is
just the result of split_symbols.

tests: tokenize: Test location structure ...

I didn't think to test this and it was giving off mutmut errors.
In retrospect it's kind of vital we test the equality check if we're
going to use it to validate tests.

tests: tokenize: Fix test only drawing whitespace

tokenize: Fix no mutate pragmas

tokenize: Add location to symbols ...

This isn't used right now but will be soon.

src: tokenize: Use symbol objects for symbols ...

This will be useful for when we add line numbers.

src: tokenize: Don't join whitespaces when splitting ...

This will be useful later when we need to track line numbers.

make: Upgrade pip when making the venv

tests: Use python-xdist for faster tests

Add mutmut for mutation testing ...

I haven't added a target for this yet but it's worth just adding it.

Example invocation: mutmut run --paths-to-mutate src/tokenize.py

tests: Add SPDX license headers

src: tokenize: Add some function comments

src: tokenize: Always append current buffer ...

Current will always have data in its buffer, so append it.

Bug found by mutmut.

tests: Add pytest-randomly

src: tokenizer: Add beginning of new tokenizer

make: Run tidy first to avoid flake8 errors

Change license to LGPL-2.1-only

tests: parse: Remove unused integers include ...

Found by flake8.

make: Add 'check' target ...

This is intended to be run before comitting changes.

tests: lexer: Drop error testing code ...

This code is awful:

- It reaches across multiple layers of abstractions
- It does a lot of string splitting and joining to rebuild code
- It only tests very specific cases because the main code is broken

Just dump it for now and start over.