feat(instances): a VM's stats in one grid, its logs a switch away

The Stats tab stacked one large card per chart, so a VM with a few
devices made a long page, and its "Real Time" and "Logs" sub-tabs were
shown to every user although only a superuser may read the logs. The
owner chose the layout from rendered options: a state line, CPU and
memory side by side, one chart per NIC and disk below, each with its
latest reading next to its title, and a small Graphs/Logs switch for
superusers.

Codex reviewed the tab; this is fixed:

- Memory is shown in MiB (it was labelled MB), and its axis grows to
  the RSS when the RSS passes the balloon size instead of clipping it.
- The CPU reading says it is of the host's CPUs.
- A NIC is titled by its MAC, not an invented "eth0", and its readings
  are matched to its chart by the MAC: they were matched by position, so
  removing a NIC while the page was open moved the next one's readings
  into its chart.
- A VM that is not running says nothing is measured.
- The logs load whenever the Logs view is shown, by keyboard too; an
  empty answer says "None" and a failed one says so, instead of an
  empty table. The tab shows the latest 50 rows, with a link to all of
  the VM's rows on the Logs page.
- The VM's header shows memory in MiB; it said MB.

vrtManager/tests/test_usage.py

@@ -86,8 +86,8 @@ class UsageTestCase(unittest.TestCase):
         self.assertEqual(
             result["disks"], [{"dev": "vda", "rd": 1000, "wr": 3000}, {"dev": "vdb", "rd": 2000, "wr": 6000}]
         )
-        # bits; the NIC without a target is not measured and keeps its place
-        self.assertEqual(result["nics"], [{"dev": 0, "rx": None, "tx": None}, {"dev": 1, "rx": 800, "tx": 400}])
+        # bits; the NIC without a target is not measured
+        self.assertEqual(result["nics"], [{"mac": "52:54:00:00:00:01", "rx": None, "tx": None}, {"mac": "52:54:00:00:00:02", "rx": 800, "tx": 400}])
         self.assertEqual(result["sample"]["counters"][3], 101.0)
 
     def test_since_the_previous_sample_without_waiting(self):
@@ -98,7 +98,7 @@ class UsageTestCase(unittest.TestCase):
         self.time.sleep.assert_not_called()
         self.assertEqual((result["cpu"], result["window"]), (12.5, 9.5))
         self.assertEqual(result["disks"][1], {"dev": "vdb", "rd": 2000, "wr": 6000})  # per second
-        self.assertEqual(result["nics"][1], {"dev": 1, "rx": 800, "tx": 400})
+        self.assertEqual(result["nics"][1], {"mac": "52:54:00:00:00:02", "rx": 800, "tx": 400})
         self.assertEqual(result["sample"]["counters"][3], 110.5)
 
     def test_a_sample_of_another_run_host_or_devices_is_not_used(self):
@@ -169,7 +169,7 @@ class UsageTestCase(unittest.TestCase):
                     {
                         "cpu": 0,
                         "disks": [{"dev": "vda", "rd": 0, "wr": 0}, {"dev": "vdb", "rd": 0, "wr": 0}],
-                        "nics": [{"dev": 0, "rx": 0, "tx": 0}, {"dev": 1, "rx": 0, "tx": 0}],
+                        "nics": [{"mac": "52:54:00:00:00:01", "rx": 0, "tx": 0}, {"mac": "52:54:00:00:00:02", "rx": 0, "tx": 0}],
                     },
                 )