Improve behaviour when multiple application instances are created

[mvaligursky]

At the moment some functionality needs to execute inside the update part of the application for it to work correctly, for example:

• getApplication()
• GraphicsDeviceAccess.get()

This makes it complicated to call engine's functionality from outside of the update.

Specific example: https://forum.playcanvas.com/t/instantiaterenderentity-fails-with-multiple-application-instances/33421