QCamera is missing several reset-functions

The QCamera API is missing several resetX() methods for most properties, this includes the corresponding QML bindings. For most properties, this is not directly a problem because the default value is a literal value and is documented. This is also not necessarily a problem from a C++ point of view, where other default values are just default-constructed classes.

It is somewhat problematic in QML, because you cannot create a default-constructed QCameraDevice or QCameraFormat in QML. This means you effectively cannot choose to go back to choosing default device if you ever choose something that is not default device.

For consistency I believe we should expose all the resetProperty() methods and have corresponding QML bindings. An initial fix would involve only doing so for properties where the default-value cannot be specified in QML.