**Summary** Instead of emitting a bogus token per char, we now only emit
on single last bogus token. This leads to much more concise output.
**Test Plan** Updated fixtures
## Summary
Allows for proper lexing of tokens like `->`.
The main challenge is to ensure that our forward and backwards
representations are the same for cases like `===`. Specifically, we want
that to lex as `==` followed by `=` regardless of whether it's a
forwards or backwards lex. To do so, we identify the range of the
sequential characters (the full span of `===`), lex it forwards, then
return the last token.
## Test Plan
`cargo test`
## 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 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`.