add arm64 nodesets

- CentOS 8
- Debian Buster
- Ubuntu Focal

Change-Id: I767d4a33433c245b4576db95b1aad8042d7ff70e

zuul.d/nodesets.yaml

@@ -11,12 +11,24 @@
       - name: centos-8
         label: centos-8
 
+- nodeset:
+    name: centos-8-arm64
+    nodes:
+      - name: centos-8-arm64
+        label: centos-8-arm64
+
 - nodeset:
     name: debian-buster
     nodes:
       - name: debian-buster
         label: debian-buster
 
+- nodeset:
+    name: debian-buster-arm64
+    nodes:
+      - name: debian-buster-arm64
+        label: debian-buster-arm64
+
 - nodeset:
     name: debian-stable
     nodes:
@@ -59,6 +71,12 @@
       - name: ubuntu-bionic-arm64
         label: ubuntu-bionic-arm64
 
+- nodeset:
+    name: ubuntu-focal-arm64
+    nodes:
+      - name: ubuntu-focal-arm64
+        label: ubuntu-focal-arm64
+
 - nodeset:
     name: ubuntu-focal
     nodes: