Add clipboard source to edit image intent

Allows image editing apps to show different UI based on whether
the image came from the clipboard overlay UI or not.

Bug: 217722654
Test: manual (no change without corresponding change to the editing
app; tested that with that change screenshots and clipboard edit
intents are treated differently)

Change-Id: I5ccb8e20de625d05ad71357330f07ef2773f3556