feat(eslint-plugin): [prefer-readonly] private fields support

[Jamesernator]

PR Checklist

• Addresses an existing open issue: fixes Enhancement: [prefer-readonly] check #private class fields #7126
• That issue was marked as accepting prs
• Steps in Contributing were taken

Overview

This adds private field support to prefer-readonly with the same behaviour as for classic TS private properties.

The tests are just duplicates of the existing tests, but with private name replaced with #name.

[typescript-eslint]

Thanks for the PR, @Jamesernator!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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✅ Successfully ran 19 targets

• nx test eslint-plugin --coverage=false
• nx test scope-manager --coverage=false
• nx run types:build
• nx test type-utils --coverage=false
• nx test visitor-keys --coverage=false
• nx run repo-tools:postinstall-script
• nx test rule-schema-to-typescript-types --coverage=false
• nx test utils --coverage=false
• nx test typescript-estree --coverage=false
• nx test parser --coverage=false
• nx test eslint-plugin-internal --coverage=false
• nx test ast-spec --coverage=false
• nx test eslint-plugin-tslint --coverage=false
• nx test repo-tools --coverage=false
• nx run-many --target=typecheck --parallel
• nx run-many --target=lint --parallel
• nx run integration-tests:test
• nx run eslint-plugin:generate:configs
• nx run-many --target=build --parallel --exclude=website --exclude=website-eslint

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[JoshuaKGoldberg]

+5/-1 in implementation
+907 in tests

Love it 😂. Super thorough tests - nicely done! 👏

Just requesting changes on a bit of docs too please. Thanks!

[JoshuaKGoldberg]

👋 Hey @Jamesernator! Just checking in, is this still something you have time for? No worries if not - I just don't want to leave it hanging.

[Jamesernator]

👋 Hey @Jamesernator! Just checking in, is this still something you have time for? No worries if not - I just don't want to leave it hanging.

I've added a small docs change to mention it now affects both typescript private modifiers and private fields.

[JoshuaKGoldberg]

Great thanks! If you re-request review through the GitHub UI we'll be notified to take a look. Otherwise we don't always go back to PRs.

[JoshuaKGoldberg]

Awesome, thanks! The tests are just as awesomely thorough as before. 🚀