Support /dev/vda in hardware.csv for tinkerbell

When deploy EKSA on KVM machines with Tinkerbell, disk is marked as /dev/vda in [hardware.csv](https://anywhere.eks.amazonaws.com/docs/reference/baremetal/bare-preparation/#disk).

The Tinkerbell action generated would be invalid in this case.

Expected disk of of write-netplan action: /dev/vda2.
Actual: /dev/vda

EKSA version: v0.15.1

Related: https://github.com/tinkerbell/tink/blob/187f9a6c181fa1560282b97d2fb4689f48e1e62e/internal/workflow/template_funcs.go#L13

Trace how the disk value from hardware.csv reaches the generated Tinkerbell write-netplan action, using the related Tinkerbell template_funcs.go reference for context. Confirm that KVM disks using /dev/vda produce the expected /dev/vda2 value rather than /dev/vda.

Written by the indexing model from the issue text.