[Feature Request]: enhance UX on image import, replace "Registry"

Feature description

There is one confusing dialog that has caused misery at customer and partner. It's small change, but UI is a bit misleading ATM. I've seen failures to import image in different ways, as the term "Repository" and "Name" are misleading. This dialog:

First of all, the word repository typically means server url like quay.io, registry.access.redhat.com. So people put those there, and enter the name of image like image:tag into the "name" field, as it can be read that way. Another error I've seen is to put http:// or https:// to "Repository" field.

Describe alternatives you've considered

In minimum, I'd change the Repository -text to "Image URL". Then I'd have an example there, like:

Image URL, e.g.: repository.com:5000/path/image:tag

Anything else?

I've heard from Max Murakami in slack that actually the example of repository.com:5000/path/image:tag is bad, as there is a bug that the dialog will grab anything after first colon as tag. That should be fixed while at it, the regexp should only take anything after the last colon as tag.