fix: Support legacy schema properties

[mdjermanovic]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

Updates @eslint/compat utility to support legacy schema property of rules.

What changes did you make? (Give an overview)

Updated fixupRule() to copy top-level schema property into rule's meta object.

This covers:

• Legacy function-style rules, which were allowed to specify schema as schema property of the function.
• Object-style rules that were mistakenly specifying schema as top-level schema property, which was never officially supported but used to work in ESLint < 9.

Related Issues

Fixes #127

I tested this with eslint-plugin-fp and eslint-plugin-filenames rules mentioned in the original issue.

Is there anything you'd like reviewers to focus on?

[fasttime]

LGTM, thanks! Leaving open until Monday in case someone else wants to review.

[nzakas]

LGTM. Thanks!