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/bash.go

@@ -0,0 +1,42 @@
+package testing
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	"github.com/actions-runner-controller/actions-runner-controller/testing/runtime"
+)
+
+type ScriptConfig struct {
+	Env []string
+
+	Dir string
+}
+
+type Bash struct {
+	runtime.Cmdr
+}
+
+func (k *Bash) RunScript(ctx context.Context, path string, cfg ScriptConfig) error {
+	abs, err := filepath.Abs(path)
+	if err != nil {
+		return err
+	}
+
+	if _, err := k.CombinedOutput(k.bashRunScriptCmd(ctx, abs, cfg)); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (k *Bash) bashRunScriptCmd(ctx context.Context, path string, cfg ScriptConfig) *exec.Cmd {
+	cmd := exec.CommandContext(ctx, "bash", path)
+	cmd.Env = os.Environ()
+	cmd.Env = append(cmd.Env, cfg.Env...)
+	cmd.Dir = cfg.Dir
+
+	return cmd
+}