qdev-monitor: avoid QemuOpts in QMP device_add

Merge Request Required Information

Summary of Changes

The virtio-blk device's iothread-vq-mapping parameter is dropped silently by device_add. This is due to how device_add is implemented using QemuOpts. These patches drop QemuOpts so that the parameter is passed through correctly.

I have also included two fixes by Kevin that are related:

• "tests/avocado/hotplug_blk: Fix addr in device_add command" fixes a device_add test failure that is related to QemuOpts
• "qdev: Fix set_pci_devfn() to visit option only once" fixes an assertion failure. I'm not sure if this one is strictly necessary but it was merged together with the previous fix.

Approved Development Ticket(s)

Resolves: RHEL-43412
Jira: https://issues.redhat.com/browse/RHEL-43412