Fix naming convention in Windowing API by using camelCase for public properties

Actual results: 

Properties in Windowing.ResolutionChangedEventArgs and Windowing.PositionChangedEventArgs are using PascalCase.

They need to use camelCase, as pointed out [Internal link].

Expected results: 

Properties in Windowing.ResolutionChangedEventArgs and Windowing.PositionChangedEventArgs are using camelCase.

.mem.xml and .api files are updated accordingly.

Reproducible with versions: 

6000.4 and 6000.5

Notes:

This is only a property naming change in order to match the Unity public API guidelines.