Improve logic and reduce failures on personal repos

[roshkhatri]

This would resolve the issue where the build workflow fails for personal repos where all or some secrets are not saved.

Also added a change where maintainers can publish multiple versions for the workflow triggers. This comes in handy when we have CVE fixes for base image or any other components which are not necessarily tied with valkey versions.

this workflow tests this all these changes: https://github.com/roshkhatri/valkey-container/actions/runs/22168758033

1. input multiple versions
2. Able to publish to the image repositories where partial secrets are set and the WFs wont fails.

[Nikhil-Manglore]

LGTM

[zuiderkwast]

Conceptually LGTM. I don't know this workflow well enough so it's better to rely on other reviewers (such as Nikhil).