feat: VM snapshots and reboot_host through the API

get_vm_snapshots, create_vm_snapshot, delete_vm_snapshot and
rollback_vm_snapshot for VMs and containers, so netOrk's snapshot view
works on Proxmox as it does on VMware. Proxmox lists the live state as a
pseudo-snapshot named "current"; it is never reported or addressable.
Containers have no RAM state, so include_memory is ignored for them.

reboot_host() restarts the node with POST /nodes/{node}/status
command=reboot instead of /sbin/reboot over SSH.

napalm_proxmox/driver.py

@@ -50,6 +50,7 @@ from napalm_proxmox.lldp_mixin import ProxmoxLLDPMixin
 from napalm_proxmox.config_mixin import ProxmoxConfigMixin
 from napalm_proxmox.vm_mixin import ProxmoxVMMixin
 from napalm_proxmox.vm_contract_mixin import ProxmoxVMContractMixin
+from napalm_proxmox.vm_snapshot_mixin import ProxmoxVMSnapshotMixin
 from napalm_proxmox.vm_provision_mixin import ProxmoxVMProvisionMixin
 from napalm_proxmox.routing_mixin import ProxmoxRoutingMixin
 from napalm_proxmox.system_mixin import ProxmoxSystemMixin
@@ -71,6 +72,7 @@ class ProxmoxDriver(
     ProxmoxConfigMixin,
     ProxmoxVMMixin,
     ProxmoxVMContractMixin,
+    ProxmoxVMSnapshotMixin,
     ProxmoxVMProvisionMixin,
     ProxmoxRoutingMixin,
     ProxmoxSystemMixin,