build: split into monorepo with separate packages

[JoshuaKGoldberg]

PR Checklist

• [x] Addresses an existing issue: fixes #1341; fixes #1317; fixes #1318
• [x] That issue was marked as status: accepting prs

Overview

Splits the large general-purpose TypeStat package into two:

• ts-enhance: Improves a project's TypeScript code by creating and improving types. 💗
• ts-initialize: Converts a project from JavaScript to TypeScript in as few changes as possible. 💝

It additionally publishes a typestat-utils package for shared code.

Generally onboards to create-typescript-app too. I figured this was a good time to do it, and test out what a monorepo with CTA would look like.

Checklist to un-draft:

• [x] Figuring out package naming
• [x] Splitting out package responsibilities
• [x] Finalize setting up workspace tasks and TSConfig project references
• [x] Passing build
• [x] Some passing tests
• [x] Figuring out monorepo/repository naming
• [ ] Resolved created TODOs (especially around shared utils)
• [ ] All passing tests
• [ ] Trying it out as a package
• [ ] Discovered issues from ☝️
• [ ] One final docs + proofreading push

[JoshuaKGoldberg]

I'm going to work on turning https://github.com/JoshuaKGoldberg/emoji-blast into a monorepo (https://github.com/JoshuaKGoldberg/emoji-blast/issues/172 -> https://github.com/JoshuaKGoldberg/emoji-blast/pull/206) first to try out the tooling in that repository first. Then once that's done and stable, I'll take its learnings here.