v-m: alerts: Add alert for temperatures

After the incident this week with the CPU overheating on _vmhost1_, I
want to make sure I know as soon as possible when anything is starting
to get too hot.

victoria-metrics/alerts.yml

@@ -141,3 +141,10 @@ groups:
       - ignoring (instance) group_right (scope) (patroni_xlog_replayed_location != 0)
       > 10240
     for: 10m
+
+- name: Temperature
+  rules:
+  - alert: High Temperature
+    expr: >-
+      {__name__=~"collectd_.*_temperature", sensors!~"i350bb.*"} > 80
+    for: 10m