Preflight check to validate folder for ETCD machines exist

[abhinavmpandey08]

What would you like to be added: vSphere Folder checks are already there for control plane and worker nodes. Add the same logic for ETCD machines.

CAPV logs:

E0906 17:24:06.570332       1 controller.go:317] controller/vspherevm "msg"="Reconciler error" "error"="failed to reconcile VM: folder '/SDDC-Datacenter/vm/capv/abhnvp' not found" "name"="abhnvp-etcd-ndrx9" "namespace"="eksa-system" "reconciler group"="infrastructure.cluster.x-k8s.io" "reconciler kind"="VSphereVM" 

EKS Anywhere version: v0.11.1

Why is this needed: Preflight improvements