Port VM autobackups into pvcworkerd with snaps

Moves VM autobackups from being in-CLI to being handled by the
pvcworkerd system on the primary coordinator. Turns the CLI autobackup
command into an actual API client endpoint rather than having its logic
in the CLI.

In addition, modifies the new autobackup to leverage the new "pvc vm
snapshot" function set, just with special snapshot names. This helps
automate this within the new snapshot scaffolding.

client-cli/pvc/lib/vm.py

@@ -595,6 +595,24 @@ def vm_import_snapshot(
     return get_wait_retdata(response, wait_flag)
 
 
+def vm_autobackup(config, email_recipients=None, force_full_flag=False, wait_flag=True):
+    """
+    Perform a cluster VM autobackup
+
+    API endpoint: POST /vm//autobackup
+    API arguments: email_recipients=email_recipients, force_full_flag=force_full_flag
+    API schema: {"message":"{data}"}
+    """
+    params = {
+        "email_recipients": email_recipients,
+        "force_full": force_full_flag,
+    }
+
+    response = call_api(config, "post", "/vm/autobackup", params=params)
+
+    return get_wait_retdata(response, wait_flag)
+
+
 def vm_vcpus_set(config, vm, vcpus, topology, restart):
     """
     Set the vCPU count of the VM with topology