Move from Cloudbuild to Github Actions

[inFocus7]

We should move our tests and codegen away from cloudbuilders onto github actions, using the kubernetes + node version that we depend on (go.mod, k8s.io). This would make dev life easier, especially when needing to update test clusters, such as updating kubernetes version.

• Note: I initially tried to do this when upgrading our k8s to 1.26, but failed to do so. An issue encountered was a permissions issue, since our Makefile commands (ex. update-code-generator) create files in folders we don't have ready access to.
• Note 2: k8s go mod dependencies are in the form 0.XY, but they represent Kubernetes version 1.XY.