Refactor image build and manifest push process

[0xaravindh]

What type of PR is this?

/kind cleanup

What this PR does / Why we need it:

Which issue(s) this PR fixes:

Works on #3978

Special notes for your reviewer:

[agones-bot]

Build Succeeded 🥳

Build Id: 7b59a234-6ffc-438a-a057-e6980c1f88a1

The following development artifacts have been built, and will exist for the next 30 days:

• image: us-docker.pkg.dev/agones-images/ci/agones-controller:1.48.0-dev-1ebe0d9
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.48.0-dev-1ebe0d9
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.48.0-dev-1ebe0d9-linux
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.48.0-dev-1ebe0d9
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.48.0-dev-1ebe0d9
• Linux C++ SDK (build): agonessdk-1.48.0-dev-1ebe0d9-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.48.0-dev-1ebe0d9.zip

A preview of the website (the last 30 builds are retained):

• https://1ebe0d9-dot-preview-dot-agones-images.appspot.com/

To install this version:

git fetch https://github.com/googleforgames/agones.git pull/4118/head:pr_4118 && git checkout pr_4118
helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.48.0-dev-1ebe0d9