feat!: a VM's vmid is a string, and its config can describe its hardware

VMDict.vmid and VMConfigDict.vmid were int. Proxmox numbers its guests,
but VMware identifies a VM by UUID, which an int cannot hold. The
provisioning dicts already carried vmid as a string; the read side now
matches. Proxmox reports "100".

VMConfigDict gains optional hardware details -- os_name, cpu_type,
sockets, cores_per_socket, firmware, machine and passthrough (PCI/USB,
as VMPassthroughDict) -- so netOrk's VM hardware view can be filled by
any hypervisor instead of reading Proxmox's raw config through the
driver's private API.

Also fixes the README's hypervisor example, which still named the
pre-contract snapshot_create.

BREAKING CHANGE: VMDict.vmid and VMConfigDict.vmid are str.

README.md

@@ -238,7 +238,7 @@ class ProxmoxDriver(HypervisorDriver):
         # return List[VMDict]
         ...
 
-    def snapshot_create(self, name, snapshot, description="", include_memory=False):
+    def create_vm_snapshot(self, name, snapshot, description="", include_memory=False):
         ...
 ```