add HV Monitor, a generic means for monitoring hypvervisors (#14218)

* add HV::Monitor support

* document hv monitor

* add HV Monitor tests

* style cleanup

* fix a few missed style items

* test fix

* more test cleanup

* more minor test tweaks

* more test cleanup

* more test tweaking

* test ordering fix all done... hopefully

* more test cleanup

* minor formatting change

includes/html/graphs/application/hv-monitor_pcpu.inc.php

@@ -0,0 +1,28 @@
+<?php
+
+$name = 'hv-monitor';
+$unit_text = 'Memory Usage %';
+$colours = 'psychedelic';
+$dostack = 0;
+$printtotal = 0;
+$addarea = 0;
+$transparency = 15;
+
+if (isset($vars['vm'])) {
+    $rrd_filename = Rrd::name($device['hostname'], ['app', $name, $app->app_id, 'vm', $vars['vm']]);
+} else {
+    $rrd_filename = Rrd::name($device['hostname'], ['app', $name, $app->app_id]);
+}
+
+$rrd_list = [];
+if (Rrd::checkRrdExists($rrd_filename)) {
+    $rrd_list[] = [
+        'filename' => $rrd_filename,
+        'descr'    => 'CPU%',
+        'ds'       => 'pcpu',
+    ];
+} else {
+    d_echo('RRD "' . $rrd_filename . '" not found');
+}
+
+require 'includes/html/graphs/generic_multi_line.inc.php';