Remove public currentCameraPositionState property

Compose 4.3.0

#262 introduced a _public_ currentCameraPositionState property. I don't think this was a good idea from an architectural standpoint, as this allows & suggests configuring the map from inside the map subcomposition by user code. Map configuration is generally intended to be done at the top level via parameters of the `GoogleMap()` composable. `CameraPositionState` is one of the parameters passed to `GoogleMap()`, duplicating responsibilities for CameraPositionState configuration.

If user code does need access to CameraPositionState from inside the subcomposition it can pass it down itself in whatever form it deems most appropriate: read-only position, read/write state, or some other kind of wrapper; captured lambda variable, parameter, or CompositionLocal. These decisions need to be left to user code.