feat: re-implement the way qemu disks are handled

[hestiahacker]

These changes were pulled from Tinyblargon's branch which was out of sync with the Telmate master branch. I merely dealt with the merge conflicts so we could re-submit a new merge request that can be applied cleanly.

The original merge request is at #794

I have also tested this and verified that these changes fix #887

[Tinyblargon]

@hestiahacker First of thank you for re-basing this.

@mleone87
There are a few bugs with my original code #794, which I've been patching over the last week.
Once this PR gets merged I'll be able to apply my patches.
These patches would consist of:

• fixed panics in weird edge cases.
• added back features that where supported by the old disk schema wwn property for example.
• improved validator logic.
• diff incorrectly, forgot to read some properties into the data structure.

Some of the bugs where in the upstream proxmox Library Telmate/proxmox-api-go#292

[MaartendeKruijf]

@Tinyblargon could you rebase onto this commit and apply your patches that would be much cleaner as to separate PR's?

[hestiahacker]

This MR has been superseded by #892

As best I can tell, MR 892 has all these changes (and more) so I'm closing this MR.