feat: move all ESLint configuration into files-based blocks (#2291)

## PR Checklist

- [x] Addresses an existing open issue: fixes #2275
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

Simplifies the `extensions` type for `blockESLint` to no longer allow
strings, and to require that objects have `files`. This way all
plugins/rules entries are scoped to specific files.

As a nice side effect, sorting of groups is a little simpler. It's
"just" an alphabetical sort of the targeted files. See the new
`processForSort`.

🎁

Author: JoshuaKGoldberg

eslint.config.js

@@ -27,19 +27,16 @@ export default defineConfig(
 		ignores: ["**/*.snap", "coverage", "lib", "node_modules", "pnpm-lock.yaml"],
 	},
 	{ linterOptions: { reportUnusedDisableDirectives: "error" } },
-	eslint.configs.recommended,
-	comments.recommended,
-	jsdoc.configs["flat/contents-typescript-error"],
-	jsdoc.configs["flat/logical-typescript-error"],
-	jsdoc.configs["flat/stylistic-typescript-error"],
-	jsonc.configs["flat/recommended-with-json"],
-	markdown.configs.recommended,
-	n.configs["flat/recommended"],
-	packageJson.configs.recommended,
-	perfectionist.configs["recommended-natural"],
-	regexp.configs["flat/recommended"],
 	{
 		extends: [
+			comments.recommended,
+			eslint.configs.recommended,
+			jsdoc.configs["flat/contents-typescript-error"],
+			jsdoc.configs["flat/logical-typescript-error"],
+			jsdoc.configs["flat/stylistic-typescript-error"],
+			n.configs["flat/recommended"],
+			perfectionist.configs["recommended-natural"],
+			regexp.configs["flat/recommended"],
 			tseslint.configs.strictTypeChecked,
 			tseslint.configs.stylisticTypeChecked,
 		],
@@ -76,11 +73,13 @@ export default defineConfig(
 			"object-shorthand": "error",
 			"operator-assignment": "error",
 		},
-		settings: {
-			perfectionist: { partitionByComment: true, type: "natural" },
-			vitest: { typecheck: true },
-		},
+		settings: { perfectionist: { partitionByComment: true, type: "natural" } },
+	},
+	{
+		extends: [jsonc.configs["flat/recommended-with-json"]],
+		files: ["**/*.json"],
 	},
+	{ extends: [markdown.configs.recommended], files: ["**/*.md"] },
 	{
 		extends: [tseslint.configs.disableTypeChecked],
 		files: ["**/*.md/*.ts"],
@@ -90,6 +89,7 @@ export default defineConfig(
 		extends: [vitest.configs.recommended],
 		files: ["**/*.test.*"],
 		rules: { "@typescript-eslint/no-unsafe-assignment": "off" },
+		settings: { vitest: { typecheck: true } },
 	},
 	{
 		extends: [yml.configs["flat/standard"], yml.configs["flat/prettier"]],
@@ -106,4 +106,5 @@ export default defineConfig(
 			],
 		},
 	},
+	{ extends: [packageJson.configs.recommended], files: ["package.json"] },
 );