Added needed call of google-github-actions/auth with credentials and changed version of google-github-actions calls

[dundejan]

Why:

Based on my own following the tutorial and usage of .github/workflows/main.yml, I found out, that there is needed to call the auth from google-github-actions for the workflow to work properly. Also the noted versions of google-github-actions were not readable, resp. their meaning was not explained and was not obvious.

When I was solving my problem, I started a discussion at community forum here: could not load the default credentials error in deploy action to GKE, where can be seen and explained the problematic part, that leads me to this little modification.