Fixes various issues in vSphere Terraform code (#8178)

* Fixes various issues in vSphere Terraform code

Provided to address various shortcomings and to fix the following
issue in upstream Kubespray:

https://github.com/kubernetes-sigs/kubespray/issues/8176

* Resolves Terraform formatting issues

* Sets default prefix to human-readable name

* Documents new default prefix in README

contrib/terraform/vsphere/output.tf

@@ -23,7 +23,7 @@ output "vsphere_network" {
 }
 
 output "vsphere_folder" {
-  value = terraform.workspace
+  value = var.folder
 }
 
 output "vsphere_pool" {