On opening a new series we need to:

 * create new repositories seeded from the unstable branches
  * ubuntu-<series>
  * ubuntu-<series>-meta
  * ubuntu-<series>-signed

 * mainline builds
  * lib-build: add new series to ubuntu_series=""
  * cod-source-trigger: add new series to series lists

 * cve-tools
  * cves-autotriage.conf: add new series to series list
  * cve-matrix/Makefile.combo: add new series to PARTS_linux