Enable assertion functions in React Native GitHub (#59090)

Summary:
Pull Request resolved: #59090

Enable `experimental.assertion_functions` and `experimental.disable_invariant_special_casing` in `react-native-github/.github.flowconfig`.

Add local libdefs for `invariant` and `invariant/invariant` returning `asserts condition`, and ignore `node_modules/invariant/**` so the package's own types cannot override them.

Changelog: [Internal]

___

landed-with-radar-review

Differential Revision: D125271821

fbshipit-source-id: 23672b08893644b38fa00dc378eb72c435912604

Author: panagosg7

.flowconfig

@@ -16,6 +16,7 @@ packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeEnumTurboModul
 **/*.windows.js
 
 **/node_modules/resolve/test/resolver/malformed_package_json/package.json
+**/node_modules/invariant/**
 
 ; Checked-in build output
 packages/debugger-frontend/dist/**
@@ -52,6 +53,9 @@ experimental.multi_platform=true
 experimental.multi_platform.extensions=.ios
 experimental.multi_platform.extensions=.android
 
+experimental.assertion_functions=true
+experimental.disable_invariant_special_casing=true
+
 munge_underscores=true
 
 module.name_mapper='^react-native$' -> '<PROJECT_ROOT>/packages/react-native/index.js'

flow-typed/npm/invariant_v2.x.x.js

@@ -0,0 +1,23 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+declare module 'invariant' {
+  declare module.exports: (
+    condition: unknown,
+    format?: string,
+    ...args: Array<unknown>
+  ) => asserts condition;
+}
+
+declare module 'invariant/invariant' {
+  import typeof Invariant from 'invariant';
+
+  declare module.exports: Invariant;
+}