Use Updated Android Locale API (#30701)

Summary:
This change migrates fetching locale information from the deprecated Android locale api to the new locale api on sdk version 30+. The old api was deprecated some time ago and should not be used.

https://developer.android.com/reference/android/content/res/Configuration#locale

## Changelog

[Android] [Changed] - Use new Locale API on Android 11 (API 30)+

Pull Request resolved: #30701

Test Plan:
```js
if (Platform.OS === 'android') {
  locale = NativeModules.I18nManager.localeIdentifier; // returns ex. 'EN_us'
}
```

Reviewed By: mdvacca

Differential Revision: D30821396

Pulled By: lunaleaps

fbshipit-source-id: 31622cd9c71c6057ff98ab5245898bc687b5ac60

Author: Aaron Grider

ReactAndroid/src/main/java/com/facebook/react/modules/i18nmanager/I18nManagerModule.java

@@ -8,6 +8,7 @@
 package com.facebook.react.modules.i18nmanager;
 
 import android.content.Context;
+import android.os.Build;
 import com.facebook.fbreact.specs.NativeI18nManagerSpec;
 import com.facebook.react.bridge.NativeModule;
 import com.facebook.react.bridge.ReactApplicationContext;
@@ -36,7 +37,12 @@ public String getName() {
   @Override
   public Map<String, Object> getTypedExportedConstants() {
     final Context context = getReactApplicationContext();
-    final Locale locale = context.getResources().getConfiguration().locale;
+    final Locale locale;
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+      locale = context.getResources().getConfiguration().getLocales().get(0);
+    } else {
+      locale = context.getResources().getConfiguration().locale;
+    }
 
     final Map<String, Object> constants = MapBuilder.newHashMap();
     constants.put("isRTL", sharedI18nUtilInstance.isRTL(context));