[TIMOB-28369] Android: Add Ti.UI.overrideUserInterfaceStyle property

*Summary:* We should add a new writable Ti.UI.overrideUserInterfaceStyle property that allows you to force the app to use a dark or light theme instead of using the system assigned theme. If this property is assigned the [Ti.UI.USER_INTERFACE_STYLE_UNSPECIFIED](https://docs.appcelerator.com/platform/latest/#!/api/Titanium.UI-property-USER_INTERFACE_STYLE_UNSPECIFIED) constant (the default), then the app will use the system theme instead. The existing read-only [Ti.UI.userInterfaceStyle](https://docs.appcelerator.com/platform/latest/#!/api/Titanium.UI-property-userInterfaceStyle) property needs to be its own property. If the overrideUserInterfaceStyle is set to unspecified, then the userInterfaceStyle property will reveal if the system is using the dark or light theme. *Native Implementation:* On iOS, this can be implemented via the native [UIView.overrideUserInterfaceStyle](https://developer.apple.com/documentation/uikit/uiview/3238086-overrideuserinterfacestyle?language=objc) property. On Android, this can be implemented via the Java [AppCompatDelegate.setNightMode()](https://developer.android.com/reference/androidx/appcompat/app/AppCompatDelegate#setDefaultNightMode(int)) method. *Android Example:* !AndroidExample.gif!