WIP: Add loadtest e2e test using Storm Forger

[rossf7]

Towards giantswarm/giantswarm#5264

Test is complete apart from creating the user values configmap. I'm still working through the bugs.

	// Test executes the loadtest test that checks that tenant cluster
	// components behave correctly under load. This primarily involves testing
	// the HPA configuration for Nginx Ingress Controller is correct and
	// interacts correctly with the cluster-autoscaler when it is enabled.
	//
	// The load test is performed by Stormforger. Their testapp is installed as
	// the test workload and a job is created to trigger the loadtest via their
	// CLI.
	//
	// https://github.com/stormforger/cli
	// https://github.com/stormforger/testapp
	//
	//     - Generate loadtest-app endpoint for the tenant cluster.
	//     - Enable HPA for Nginx Ingress Controller via user configmap.
	//     - Install loadtest-app chart in the tenant cluster.
	//     - Wait for loadtest-app deployment to be ready.
	//     - Install stormforger-cli chart in the tenant cluster.
	//     - Wait for stormforger-cli job to be completed.
	//     - Get logs for stormforger-cli pod with the results.
	//     - Parse the results and determine whether the test passed.
	//

[rossf7]

Stale.