Adds game server template with containerized sdk-client-test

[igooch]

What type of PR is this?

/kind feature

What this PR does / Why we need it:

This adds a game server template that includes the sdk-client-test that will be built, pushed, and tagged at the released Agones versions DEV-10 (1.34.0) to DEV-1 (1.43.0). The controller will create gameserver.yaml files for each valid Agones version. In a future PR these game servers will be created and run while installing Agones.

This PR also updates the capitalization to be consistent with Agones' use of CamelCase rather than ALL_CAPS for const values.

This PR gets rid of the go.mod and go.sum files for the upgrade test, and instead makes use of the Docker build process to create the go module when building the image. This will keep the images up to date with the latest versions of dependencies.

Which issue(s) this PR fixes:

Working on: #3795

Special notes for your reviewer:

The sdk-client-test imports agones.dev, so when building the image go.mod can only download released versions of Agones.

[agones-bot]

Build Failed 😭

Build Id: 1ef7954a-3030-4dc0-a1c0-bf181b408c35

Status: FAILURE

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[agones-bot]

Build Failed 😭

Build Id: 73f5b7a0-b291-40a8-aea7-653311017ccc

Status: FAILURE

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[agones-bot]

Build Failed 😭

Build Id: 03d6a4ce-1ff9-4173-a895-da1ea3964536

Status: FAILURE

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[agones-bot]

Build Failed 😭

Build Id: 3f667124-0cd5-413f-9e9b-7293d6f2d4f8

Status: FAILURE

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[agones-bot]

Build Succeeded 🥳

Build Id: cf9f78a9-f714-4edb-a605-0bbb07b23ac3

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:1.44.0-dev-983752b
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.44.0-dev-983752b
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.44.0-dev-983752b-linux
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.44.0-dev-983752b
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.44.0-dev-983752b
• Linux C++ SDK (build): agonessdk-1.44.0-dev-983752b-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.44.0-dev-983752b.zip

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

• https://983752b-dot-preview-dot-agones-images.appspot.com/

To install this version:

git fetch https://github.com/googleforgames/agones.git pull/3987/head:pr_3987 && git checkout pr_3987
helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.44.0-dev-983752b