Add support to select an artifact when creating an image builder

**What's it about?**

Currently, users only can upload a binary file manually even they want to create an image builder against the same file multiple times.


/area devops
/priority medium

**What's the reason why we need it?**

In the real world, users always have their own artifact server. For example, Nexus, MinIO, [Artifactory](https://jfrog.com/artifactory/), etc. It would be very inconvenient if users need to upload it manually.

So, I propose that the Image Builder allows users to choose an artifact from a server (like I mentioned before). There're a couple of things that we might need to consider:

* integration with Nexus, MinIO, etc.
* auth support
* changes from the front-end side

Please leave your comments below if there's anyone who agrees with me. Or just give me a thumb up.

**Area Suggestion**

/kind feature-request

No files, tests, or entry points are identified. Start by mapping the image-builder creation flow and how artifacts are currently uploaded, then investigate the proposed Nexus, MinIO, and Artifactory integrations and authentication requirements. Done means users can select an existing artifact from a supported server when creating an image builder, including the needed frontend changes.

Written by the indexing model from the issue text.