Enhancement: Add a console.warn to experimental-utils

[JoshuaKGoldberg]

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• I have searched for related issues and found none that match my proposal.
• I have searched the current rule list and found no rules that match my proposal.
• I have read the FAQ and my problem is not listed.

Relevant Package

utils

My proposal is suitable for this project

• I believe my proposal would be useful to the broader TypeScript community (meaning it is not a niche proposal).

Description

The @typescript-eslint/utils package used to be called @typescript-eslint/experimental-utils. We procrastinated removing the experimental- from the name for a while, then finally did it in #4139. We left the old experimental- package behind so as to not break things for people. But, it'd be good for them to stop referring to the old package name.

See this line in experimental-utils README.md:

typescript-eslint/packages/experimental-utils/README.md

Line 21 in 91d71bc

> ⚠ A future major version of this old package will `console.warn` to ask you to switch.

Now that we're working on breaking changes for our next major version, v6, we can add that console.warn in!

Proposal: in https://github.com/typescript-eslint/typescript-eslint/blob/91d71bcf6b2f822116d25b281e289fe1d5005401/packages/experimental-utils/src/index.ts, add a console.warn that says something like the text from the README.md:

typescript-eslint/packages/experimental-utils/README.md

Lines 13 to 14 in 91d71bc

	**This package is purely a re-export of `@typescript-eslint/utils`.**
	You should switch to importing from that non-experimental package instead.

Fail

n/a

Pass

n/a

Additional Info

This is a breaking change and will need to target the v6 branch.

[JoshuaKGoldberg]

Fixed in #6179.