🚀 Feature: Switch request Creations to a serializable and testable format

[JoshuaKGoldberg]

Bug Report Checklist

• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.

Overview

I'd noted in #64:

Note that this is the first Creation form that isn't directly serializable. Files and scripts can all be made JSON; requests now introduce functions. I'd been hoping to keep everything serializable - but being able to instead get nice type completion with using Octokit APIs is just more useful.

If someone wants serializable requests in the future, I suppose they could file a feature request asking for the JSON-like equivalent of this. Something like:

{
  "fetcher": "octokit",
  "method": ["rest", "repos", "update"],
  "send": {
    allow_auto_merge: true,
    // ...
  }
}

...where fancy TypeScript types determine the send data to be Parameters<typeof octokit.rest.repos.update>[0]. That's a lot more work. Perhaps a future improvement.

I also don't love that explicit id in there. Previous Creations are auto-mergable without them; this one is manual. I suppose that's also tied in with it not being serializable. Perhaps a future improvement.

Another downside of the non-serializable requests format is the not-very-informative [Function] showing up in creation snapshots. For example, in working on JoshuaKGoldberg/create-typescript-app#1775, I'm seeing the test output for a Block that creates requests as:

const creation = testBlock(blockRepositoryBranchProtection, {
	addons: {
		requiredStatusChecks: ["build", "test"],
	},
	options: optionsBase,
});

expect(creation).toMatchInlineSnapshot(`
	{
	  "requests": [
	    {
	      "id": "branch-protection",
	      "send": [Function],
	    },
	  ],
	}
`);

As a followup, I'd like to eventually pursue the avenue of a fully serializable, type-safe requests format.

Additional Info

Marking as status: blocked for the time being. It doesn't block full CTA parity. But I will want it to block a full launch.

💖