Drop some custom type guards in favor of ASTUtils

[gndelia]

As seen in some PRs created by @Belco90 , there's a utility ASTUtils in '@typescript-eslint/experimental-utils' which can replace some, but not all, of the type guards we have in our node-utils.ts file

This ticket is to review which type guards (isIdentifier, isVariableDeclarator, etc) are repeated, and drop those in favour of the ones in ASTUtils. The ones that are not available there should continue to exist with our custom implementation.

Edit: This PR should target the v4 branch

[Belco90]

Ideally, this should be done over v4 rather than master so we get rid of it everywhere 😅

[thomaslombart]

Is someone already working on it? I haven't contributed to the codebase for a while, and I'd like to get familiar with it again. I think that issue may be the best to start with 🙂

[github-actions]

🎉 This issue has been resolved in version 4.0.0-beta.1 🎉

The release is available on:

• npm package (@beta dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[github-actions]

🎉 This issue has been resolved in version 4.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀