RN: Private Package for Monorepo ESLint Rules (#51858)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/51858

Creates a new private package for the ESLint rules that are defined in the `facebook/react-native` repository for linting the monorepo itself: `react-native/eslint-plugin-monorepo`

It resides in a new `private/` directory that will be used for all private packages. I plan to move private packages over from `packages/` and `tools/`.

This also eliminates the need for the `eslint-plugin-lint` dependency in open source.

Changelog:
[Internal]

Reviewed By: cortinico

Differential Revision: D76088698

fbshipit-source-id: 697d5d91421cda4ef3f96d0497a96954cd047296