- re-evaluate the validators to be able to hide the warning after 3
seconds (the validators won't let the user select/paste an invalid
image; it's just the warning bubble that persisted)
- some small cleanups
Fixes#16210
Fixes#9966
Uses the validate function to paste images so that it concatenates the previous images.
FIxes the validate function to also accept data images.
Moves the size validation function to Utils to reuse the data path prefix constant and fix the possible crash when we try to get the size of a data image.