Previously, in the required validator, we would read the required setting directly
from attr.required, where it is set by ngRequired.
However, when the control is inside ngRepeat, ngRequired sets it only after a another digest has
passed, which means the initial validation run of ngModel does not include the correct required
setting. (Before commit 0637a2124c this would not have been a problem,
as every observed value change triggered a validation).
We now use the initially parsed value from ngRequired in the validator.
Fixes#16814Closes#16820
Martin Staffa
5ad4f5562c