UTM's Apple Script API can't be used to read specific drive configuration

I'm opening this issue to track my progress on fixing the likely broken plumbing in the API. I'm specifically looking to fix source image file retrieval via API for removable drives. I'll contribute a PR so others can benefit from the API enhancement for more robust management of the images "inserted" into them.

**Describe the issue**
I was tinkering with the UTM Apple Script API interface and found I couldn't read the `source` property of a VM to get, for example, a iso image set as the drive's source. Discussed if this was intentional with @osy on Discord, indicating this was NOT intentional.

Scope of this issue may not be limited to just Apple Script, but that's what my fix is targeting first. I'll investigate accordingly and make sure any fix covers other APIs if they're also not working as intended.

**Configuration**
* UTM Version: 5.0.3
* macOS Version: 14
* Mac Chip (Intel, M1, ...): Intel

**Crash log**
N/A

**Debug log**
N/A

**Upload VM**
N/A