Incus VMs use UTC time instead of local, breaking Windows VMs

The new Incus-based VM implementation always uses UTC time for the “real time clock” exposed to VMs.
By default, this breaks time in Windows VMs, as it will be off by one hour (or more). This did not happen in 24.10 or earlier, as there was an option to either set the time to LOCAL or UTC. The default was LOCAL. For Linux VMs, you want to use LOCAL though. So, an option is needed (again), maybe with a small explanation when to use which option.

If a “localtime” option is enabled, middleware would just need to add -rtc base=localtime to the raw.qemu config. I tested manually editing the Incus config and it works, but that config part (obviously) gets wiped by middleware if the the instance is updated/edited using the TrueNAS UI.

The incorrect time causes issues with Windows domains (Kerberos requires 5 min accuracy).
And it’ll be wrong on every startup, until Windows eventually sync time (IIRC happens via a task on Sunday for normal installs and every ~10 hours when using the Win time service).

A workaround in Windows is to create and set the RealTimeIsUniversalto 1 (search the web for more info), but this would need to be modified on all existing and new Windows VMs, which really isn’t feasible.