Add gc metrics for ZGC and ShenandoahGC

Change-Id: I518a655f4c8080a8b5b23e67d6a518b503000949

dashboards/gerrit/process/panels/gc-time.libsonnet

diff --git a/dashboards/gerrit/process/panels/gc-time.libsonnet b/dashboards/gerrit/process/panels/gc-time.libsonnet
index 16a11ac..395b6dc 100644
--- a/dashboards/gerrit/process/panels/gc-time.libsonnet
+++ b/dashboards/gerrit/process/panels/gc-time.libsonnet
@@ -39,6 +39,20 @@
     interval='1m',
   )
 )
+.addTarget(
+  prometheus.target(
+    'increase(proc_jvm_gc_time_ZGC{instance="$instance",replica="$replica"}[2m])/increase(proc_uptime{instance="$instance",replica="$replica"}[2m])',
+    legendFormat='gc time ZGC',
+    interval='1m',
+  )
+)
+.addTarget(
+  prometheus.target(
+    'increase(proc_jvm_gc_time_ShenandoahGC{instance="$instance",replica="$replica"}[2m])/increase(proc_uptime{instance="$instance",replica="$replica"}[2m])',
+    legendFormat='gc time ShenandoahGC',
+    interval='1m',
+  )
+)
 .addSeriesOverride(
   {
     alias: 'gc time G1 young gen',
@@ -63,3 +77,15 @@
     color: '#E02F44',
   }
 )
+.addSeriesOverride(
+  {
+    alias: 'gc time ZGC',
+    color: '#3274D9',
+  }
+)
+.addSeriesOverride(
+  {
+    alias: 'gc time ShenandoahGC',
+    color: '#3274D9',
+  }
+)
\ No newline at end of file