Add virtualbox-iso target

Lots of other, small quality of life improvements to build process
Output of build serial console to artifacts upon failure
Reducing verbosity of Packer, now that serial output is captured
Fixed sizing problems with the boot partitions of Ubuntu versions
Use of Mac builders for Virtualbox targets
Updating Ubuntu builders to 22.04, as well

http/ubuntu/20.04/user-data

@@ -2,12 +2,22 @@
 # vim: set ft=yaml:
 autoinstall:
   version: 1
+  apt:
+    preserve_sources_list: false
+    primary:
+      - arches: [i386, amd64]
+        uri: http://archive.ubuntu.com/ubuntu
+      - arches: [default]
+        uri: http://ports.ubuntu.com/ubuntu-ports
+    geoip: false
   network:  # Should disable networking, workaround for unattended-updates failing in install
     version: 2
   refresh-installer:
     update: no
   keyboard:
     layout: us
+    variant: ""
+    toggle: null
   storage:
     config:
       - id: drive
@@ -25,7 +35,7 @@ autoinstall:
       - id: boot-partition
         type: partition
         device: drive
-        size: 200M
+        size: 1G
         name: boot
       - id: swap-partition
         type: partition