feat: add a new MissingWord LintKind

[hippietrail]

Issues

N/A

Description

I was looking at a linter that inserts a missing word and realized that none of the LintKinds really fit, usually Usage is the closest. But we've now got easily enough linters adding missing words to warrant a new MissingWord LintKind.

This PR converts all the linters I could identify that add a missing word, whether that be always or only on some logic paths.

I also found an opportunity to make the LintKind code a little bit more DRY, and I found a debug-printf that accidentally slipped through.

I'm less that fully fluent in some of the web and desktop code that does things such as grouping LintKinds together, so would appreciate people reviewing those parts.

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.

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.