Add support for pushing "stable" images to Zalando open source registry.

[bmaher]

Description

This PR pushes those images that have passed the E2E test to Zalando's open source registry.

Motivation and Context

This is part 1 of a set of changes to allow for specifying 'stable' images in internal projects.

How Has This Been Tested?

Ran in CDP.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the code style of this project.
• I have read the CONTRIBUTING document.
• All new and existing tests passed.

[codecov-io]

Codecov Report

Merging #666 into master will increase coverage by 0.06%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #666      +/-   ##
============================================
+ Coverage     62.59%   62.65%   +0.06%     
- Complexity      517      518       +1     
============================================
  Files            45       45              
  Lines          3259     3259              
  Branches        283      283              
============================================
+ Hits           2040     2042       +2     
+ Misses         1023     1022       -1     
+ Partials        196      195       -1

[diemol]

👍

[bmaher]

👍