Ability to specify MAC address of VM during build

[mikedonleyuoy]

/kind feature

Describe the solution you'd like
Ability to specify a MAC address when creating Packer built VM to allow external IPAM to provide IP address over DHCP.

Anything else you would like to add:
In theory we might be able to achieve what we need using static IPs in autounattend.xml, but because the MAC address of network adapter isn't known, it's hard to set a static IP address and will likely cause further problems removing down the line.

Environment:
Our environment has separate IPAM and can only issue IP addresses where the MAC address is known, therefore we need to specify the MAC address as the packer build.

• packer-plugin-nutanix version (use packer plugins installed): 0.9.0
• Packer version (use packer version): 1.11
• OS (e.g. from /etc/os-release): Windows Server 2019 and 2022