Expose ImageProps from ImageComponentView's and add ImageSource type

[acoates-ms]

Description

Adding a new ImageProps object to allow querying of properties from ImageComponentViews. This also includes adding a new ImageSource type, with a ReadValue function, which can be used by custom components needing to parse ImageSource types from JS, and in future codegen of custom Props objects.

Open Question

Ideally the props would be exposed as:

runtimeclass ViewProps;
runtimeclass ImageProps : ViewProps;
 
runtimeclass ViewComponent {
 ViewProps Props {get;};
}
 
runtimeclass ImageComponent {
 ImageProps Props {get;}
}

However, I'm not sure if that kind of override is supported and didn't have much luck making it. So instead, I added a separate ImageProps property to ImageComponentView. If anyone knows how to get the above to work that would be a cleaner interface.

Microsoft Reviewers: Open in CodeFlow