bgpd: add colored extended communities support

bgpd: add colored extended communities support

add support of color extended community, conforming to RFC 9012.
This extended community will be added to the existing one, RT,SOO
and Node Target. The configuration will be made through the
route-map service.

find above a configuration example:

router bgp 65001
 bgp router-id 192.168.1.1
 no bgp ebgp-requires-policy
 no bgp network import-check
 neighbor 192.168.1.2 remote-as external
 neighbor 192.168.1.3 remote-as external
 neighbor 192.168.1.4 remote-as external
 address-family ipv4 unicast
  network 10.10.10.10/24 route-map rmap
  exit-address-family
!
  route-map rmap permit 10
   set extcommunity color 55555 200
  exit

Signed-off-by: Francois Dumontet <francois.dumontet@6wind.com>