Fleet GitRepo wizard UX improvements, new steps, fields size and banners

[torchiaf]

Summary

Fixes #13402
Fixes #13473

Occurred changes and/or fixed issues

Technical notes summary

Areas or cases that should be tested

Areas which could experience regressions

Screenshot/Video

Metadata

Repository details

Target Details

Advanced

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
• The PR has a Milestone
• The PR template has been filled out
• The PR has been self reviewed
• The PR has a reviewer assigned
• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes

[cnotv]

I don't see issues code-wise.

LGTM

[torchiaf]

@edenhernandez-suse and QA: I included only a few features from the original design:

• Warning banner on top of the Advanced step
• Steps positions and descriptions
• Added icons to Add buttons

Steps centered layout, fields size and summary will be for 2.12, considering that Wizard is in common with Charts pages