Force all PCIe devices through D3Cold

[DemiMarie]

The problem you're addressing (if any)
The only quasi-guaranteed way to reset a PCIe device is to force it through D3Cold (electrically powered off). Otherwise, there is an increased risk that state could be carried over, which could be used to compromise the next user of the device.

Describe the solution you'd like
Hold all PCIe devices in D3Cold for long enough for internal capacitors to discharge.

Where is the value to a user, and who might that user be?
All users who use PCIe pass-through to untrusted VMs, or VFIO with untrusted userspace drivers, will benefit from improved security. This includes all users of Qubes OS

Describe alternatives you've considered
None

Additional context
None

Relevant documentation you've consulted
Private communication

Related, non-duplicate issues
None