## Summary
For #6485, I need to be able to use the `SimpleTokenizer` to lex the
space between any two adjacent expressions (i.e., the space between a
preceding and following node). This requires that we support a wider
range of keywords (like `and`, to connect the pieces of `x and y`), and
some additional single-character tokens (like `-` and `>`, to support
`->`). Note that the `SimpleTokenizer` does not support multi-character
tokens, so the `->` in a function signature is lexed as a `-` followed
by a `>` -- but this is fine for our purposes.
## Summary
This PR protects against code like:
```python
from typing import Optional
import bar # ruff: noqa
import baz
class Foo:
x: Optional[str] = None
```
In which the user wrote `# ruff: noqa` to ignore a specific error, not
realizing that it was a file-level exemption that thus turned off all
lint rules.
Specifically, if a `# ruff: noqa` directive is not at the start of a
line, we now ignore it and warn, since this is almost certainly a
mistake.
## Summary
This crate now contains utilities for dealing with trivia more broadly:
whitespace, newlines, "simple" trivia lexing, etc. So renaming it to
reflect its increased responsibilities.
To avoid conflicts, I've also renamed `Token` and `TokenKind` to
`SimpleToken` and `SimpleTokenKind`.
