e2e: Cover RunnerDeployment (#668)

Previously the E2E test suite covered only RunnerSet. This refactors the existing E2E test code to extract the common test structure into a `env` struct and its methods, and use it to write two very similar tests, one for RunnerSet and another for RunnerDeployment.

testing/docker.go

@@ -0,0 +1,49 @@
+package testing
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"path/filepath"
+
+	"github.com/actions-runner-controller/actions-runner-controller/testing/runtime"
+)
+
+type Docker struct {
+	runtime.Cmdr
+}
+
+type DockerBuild struct {
+	Dockerfile string
+	Args       []BuildArg
+	Image      ContainerImage
+}
+
+type BuildArg struct {
+	Name, Value string
+}
+
+func (k *Docker) Build(ctx context.Context, builds []DockerBuild) error {
+	for _, build := range builds {
+		var args []string
+		args = append(args, "--build-arg=TARGETPLATFORM="+"linux/amd64")
+		for _, buildArg := range build.Args {
+			args = append(args, "--build-arg="+buildArg.Name+"="+buildArg.Value)
+		}
+		_, err := k.CombinedOutput(k.dockerBuildCmd(ctx, build.Dockerfile, build.Image.Repo, build.Image.Tag, args))
+
+		if err != nil {
+			return fmt.Errorf("failed building %v: %w", build, err)
+		}
+	}
+
+	return nil
+}
+
+func (k *Docker) dockerBuildCmd(ctx context.Context, dockerfile, repo, tag string, args []string) *exec.Cmd {
+	buildContext := filepath.Dir(dockerfile)
+	args = append([]string{"build", "--tag", repo + ":" + tag, "-f", dockerfile, buildContext}, args...)
+
+	cmd := exec.CommandContext(ctx, "docker", args...)
+	return cmd
+}