[TIMOB-28476] Android: Add PendingIntent constants FLAG_IMMUTABLE and FLAG_MUTABLE

*Summary:* When targeting Android 12 (aka: API Level 31), you must provide either a [FLAG_IMMUTABLE](https://developer.android.com/reference/android/app/PendingIntent#FLAG_IMMUTABLE) or [FLAG_MUTABLE](https://developer.android.com/reference/android/app/PendingIntent#FLAG_MUTABLE) when creating/getting a PendingIntent or else an exception will be thrown. This is a breaking-change made by Google. https://developer.android.com/about/versions/12/behavior-changes-12#pending-intent-mutability *To-Do:* Add the following constants to Titanium. * Ti.Android.FLAG_IMMUTABLE * Ti.Android.FLAG_MUTABLE When calling [Ti.Android.createPendingIntent()](https://developer.android.com/reference/android/app/PendingIntent#FLAG_MUTABLE), Titanium should automatically assign it the FLAG_IMMUTABLE constant unless the caller sets the FLAG_MUTABLE explicitly.