WIP: Feature/rapid cdn http3 control

TODOs:

• cleanup
• stop using QUIC, it's HTTP3 for the admin
• keep in mind about HTTP3 advertised port (do not call it QUIC port)
• add cluster global HTTP3 enabler, by default false
• add node specific HTTP3 enabler, by default cluster global HTTP3
• implicitly use haproxy-quic flavor when HTTP3 is enabled on a node
• as a consequence drop:
  • -frontend-<i>-experimental-haproxy-flavour
  • -frontend-1-experimental-haproxy-flavour
  • -frontend-1-experimental-quic-port
• test against:

{
  "only-sr": [
    "rapid-cdn",
    "erp5-zope2",
    "erp5",
    "kvm",
    "slapos-master",
    "json-schemas"
    ]
}