Major rework of RFC9234 support. My initial interpretation of the RFC was

Major rework of RFC9234 support. My initial interpretation of the RFC was
too conservative. Fixes and changes include:

- add role output to bgpctl, also adjust the capability output.
  Note, this changes the JSON output of neighbors a bit.
- adjust the config parser to enable the RFC9234 role capability when
  there is a role set. iBGP and sessions with no role will not announce
  the role capability.
- adjust the role capability announcement to be only on sessions that
  use either AFI IPv4 or IPv6 and SAFI 1 (AID_INET, AID_INET6).
- if there is an OPEN notification indicating that the role capability
  is bad only disable the capability if it is not enforced.
- Adjust capability negotiation, store remote_role on the peer since
  the neighbors role is no longer needed by the RDE.
- inject the OTC attribute on ingress only for AID_INET and AID_INET6.
  For other AIDs clear the F_ATTR_OTC_LOOP flag.
- Adjust the role logic in the RDE and use the peer->role (local role of
  the system) for all checks. Also remove the check if the role capability
  was negotiated between peers.
- In prefix_eligible() check also if the F_ATTR_OTC_LOOP flag is set.
  The RFC requires that prefixes must be considered ineligible (and not
  treat as withdraw as done before)
- When generating an UPDATE include the OTC attribute unless the AID is
  neither AID_INET or AID_INET6.

Fixes https://github.com/openbgpd-portable/openbgpd-portable/issues/51
Reported by Pier Carlo Chiodi
OK tb@