Restore `toggle-all-things-with-alt` feature #1729

It was removed in https://github.com/sindresorhus/refined-github/pull/1524 as requested in https://github.com/sindresorhus/refined-github/issues/1486, but our implementation touched more than just diffs.

Some other things that can be toggled in batch:

• resolved comments (not just reviews) e.g.: https://github.com/sindresorhus/refined-github/pull/1694#issuecomment-451926782
• review comments per-file ("Show comments" checkbox): https://github.com/sindresorhus/refined-github/pull/1896/files
• large collapsed diffs: https://github.com/sindresorhus/refined-github/issues/825