reclass: virtual: Factor out VM interface naming

reclass: virtual: Factor out VM interface naming

Define two groups of VM interface naming:
- ens3..ens6 - used by infra VMs, virtual node VMs;
- ens2..ens3 - used by VCP VMs (spawned by salt.control);

Parametrize newly defined interface names throughout the cluster
models.

While at it, add AArch64 default values for above iface names.

NOTE: baremetal clusters will be parametrized later, after common
config is factored out into <baremetal-mcp-ocata-common>.

Change-Id: I89aba9aaf85b585cc510302eb76d7810fbf60679
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>