[Kandinsky] Correct all masking documentation of Kandinsky and advertise / document the end-to-end pipelines better

[patrickvonplaten]

#4207 introduced end-to-end Kandinsky pipelines and also changed the masking behavior which arguably can be seen as a breaking change. We need to make sure that:

• 1.) All diffusers docs correctly reflect this breaking change
• 2.) All Kandinksy model cards correctly reflect this breaking change
• 3.) It would be nice if we could advertise the end-to-end pipelines a bit more (probably on the model cards)

cc @yiyixuxu could you maybe take a look here?