Sending as a reference for#2829 ->eslint/eslint#18087.

This:

1. CopiesFileEnumerator.js from ESLint's source as aFileEnumeratorIsh class
2. UsesFileEnumeratorIsh instead of the existingFileEnumerator imports inno-unused-modules.js
3. Removes any code paths that don't seem to be relevant anymore

This code is not ready to be reviewed. It doesn't preserve existing licensing/ownership. And I don't work in this repository nearly enough to be confident all of those removals were ok to remove. It's just a reference to show thatisDirectoryIgnored +isFileIgnored seems to be enough for the rule to go off of.