migrate eslint from old flatConfig compat to modern flatConfig (#13138)

Verified locally by comparing the output of
```sh
% yarn eslint --print-config src/core/__tests__/ApolloClient.test.ts >| test.lint                                                                                                                                                 
% yarn eslint --print-config src/react/hooks/useQuery.ts >| useQuery.lint                                                                                                                                                         
% yarn eslint --print-config src/core/ApolloClient.ts >| ApolloClient.lint  
```
before and after these changes.

Author: phryneas

eslint-local-rules/index.mjs

@@ -17,6 +17,8 @@ import {
   TDataTVariablesOrder,
 } from "./generics.ts";
 
+/** @type {import("eslint").ESLint.Plugin['rules']} */
+// @ts-ignore - mismatch between different plugin types, but works
 export default {
   "require-using-disposable": requireUsingDisposable,
   "require-disable-act-environment": requireDisableActEnvironment,

eslint.config.mjs

@@ -15,40 +15,37 @@ if (!process.features.typescript) {
 import path from "node:path";
 import { fileURLToPath } from "node:url";
 
-import { fixupPluginRules } from "@eslint/compat";
-import { FlatCompat } from "@eslint/eslintrc";
-import js from "@eslint/js";
+import { defineConfig, globalIgnores } from "eslint/config";
 import typescriptEslint from "@typescript-eslint/eslint-plugin";
 import tsParser from "@typescript-eslint/parser";
-import _import from "eslint-plugin-import";
+import importPlugin from "eslint-plugin-import";
 import * as mdx from "eslint-plugin-mdx";
 import globals from "globals";
 import reactHooks from "eslint-plugin-react-hooks";
+import testingLibrary from "eslint-plugin-testing-library";
 
 import localRules from "./eslint-local-rules/index.mjs";
 
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
-const compat = new FlatCompat({
-  baseDirectory: __dirname,
-  recommendedConfig: js.configs.recommended,
-  allConfig: js.configs.all,
-});
 
 /**
  * Some rules can be very costly so we only want to run them from CLI, not from the LSP.
  */
 const runExtendedRules = !!process.env.EXTENDED_RULES;
 
+/** @type {Record<string, import("eslint").ESLint.Plugin>} */
 const tsPlugins = {
-  import: fixupPluginRules(_import),
+  import: importPlugin,
   "local-rules": {
     rules: localRules,
   },
+  // @ts-ignore - slight mismatch between old and new ESLint plugin types
   "@typescript-eslint": typescriptEslint,
 };
 
-export default [
+export default defineConfig([
+  globalIgnores(["integration-tests/"]),
   {
     files: ["**/*.ts", "**/*.tsx"],
     plugins: tsPlugins,
@@ -212,16 +209,15 @@ export default [
       "local-rules/tdata-tvariables-order": "error",
     },
   },
-  ...compat.extends("plugin:testing-library/react").map((config) => ({
-    ...config,
-
+  {
     files: [
       "**/__tests__/**/*.[jt]s",
       "**/__tests__/**/*.[jt]sx",
       "**/?(*.)+(test).[jt]s",
       "**/?(*.)+(test).[jt]sx",
     ],
-  })),
+    ...testingLibrary.configs["flat/react"],
+  },
   {
     files: [
       "**/__tests__/**/*.[jt]s",
@@ -290,4 +286,4 @@ export default [
     basePath: "docs",
     ...mdx.flatCodeBlocks,
   },
-];
+]);

jsconfig.json

@@ -0,0 +1,11 @@
+{
+  "compilerOptions": {
+    "checkJs": true,
+    "strict": true,
+    "noImplicitAny": true,
+    "module": "nodenext",
+    "moduleResolution": "nodenext",
+    "allowImportingTsExtensions": true
+  },
+  "include": ["**/*.js", "**/*.mjs"]
+}

knip.config.js

@@ -22,7 +22,7 @@ const scriptEntries = Array.from(
 /** @type{import('knip').KnipConfig}*/
 const config = {
   exclude: ["optionalPeerDependencies", "unresolved"],
-  entry: []
+  entry: /**@type {string[]}*/ ([])
     .concat(packageEntries)
     .concat(scriptEntries)
     .concat([