feat: enhance the ToTo linter

[hippietrail]

Issues

N/A

Description

Previously it always flagged "to to" and only suggested "to do".

It did not cooperate with RepeatedWords to suggest dropping the second "to", since that's not possible.

It was not aware of patterns where "to to" is grammatically correct, such as after certain verbs and before a verb in the infinitive.

This PR moved the old linter out of phrase_set_corrections into a custom Rust linter.

I also added a new surrounded_by_words() method to ExprLinter that combines the existing followed_by_token() and preceded_by_word().

How Has This Been Tested?

cargo test

AI Disclosure

• I am a human and didn't use any AI.
• I used LLM features of my editor, but not an agent.
• I consulted one or more coding AIs, but didn't use an agent.
• I used an AI agent interactively.
• I am an agent or I got an agent to do the work autonomously.

I asked Google's AI to suggest how best to implement surrounded_by_words() and to write the doc comments.

If Your PR Implements or Enhances a Linter

• I made up the sentences in the unit tests.
• The sentences in the unit tests were generated by an AI.
• I'm using examples from the bug report / feature request.
• I collected real-world sentences for the unit tests.

Checklist

• I have performed a self-review of my own code
• I have added tests to cover my changes
• I have considered splitting this into smaller pull requests.