Custom component Input and output properties should be better differentiated

[gregli-msft]

In the bleow, CustomProperty1 is an Input property and CustomProperty2 is an Output property. Yet they show up the same way, which is very confusing.

Component1 As CanvasComponent:
  CustomProperty1: ="Text, Modified"
  CustomProperty2: ="Text, Modified"

It should be something closer to:

Component1 As CanvasComponent:
    CustomProperty1:
        InputDefault: ="Text, Modified"
    CustomProperty2: ="Text, Modified"

In the future, we may be supporting separated Input and Output properties:

Component1 As CanvasComponent:
    CustomProperty3:
        InputDefault: ="Text, Modified"
        Output: ="Text, Modified"

Not something blocking public preview, but we should look at this as we add the other metadata for property parameters.