Move e2e tests to golang

[adambkaplan]

Our e2e testing currently relies on bash scripting. This is fine for an initial start, but it won't scale as we start adding more sophisticated requirements before merging updates to the service.

We should move our e2e tests to golang, since the overwhelming majority of Kubernetes client libraries are written in go. Most Tekton and Kubernetes contributors are already familiar with testing using Go and the ginkgo framework. Tests can be run directly via go test, or can be packaged into a binary/container image that can then be executed on a cluster.