WIP: D2iQ Build Environment Updates.

[kaiwalyajoshi]

Change log description

Update build scaffolding for GHCR images.

• Use self-hosted runners.
• Use ghcr.io as registry.
• Remove image pushes to external org repositories like emccorp and pravega
• Use the same repository to push test images prefixed with a testimages- tag.
• Enable workflow_dispatch for CI GHA to test changes.

Purpose of the change

(e.g., Fixes #666, Closes #1234)

What the code does

(Detailed description of the code changes)

How to verify it

(Steps to verify that the changes are effective)

[kaiwalyajoshi]

This PR became an experimental testbed. closing this and pushing up results in the next one.

[kaiwalyajoshi]

Closing PR.