BIRD show bgp summary for cli

[Roman Bulakh]

Hi,

we use BIRD in our environment, and it would be very nice to have some
command like `show bgp summary` in juniper. This command show
information about peer IP, peer AS, last update, prefixes
received/best/exported and last state. 


Example:
bird> show bgp summary 
Peer                    AS Last state change   Prfx rcvd/best/export
State
X.X.X.X           asXXXX 2021-01-27          6786/6785/109000
Established   
Y.Y.Y.Y        asYYYY 2020-12-16          0/0/0
Passive BGP Error: Hold timer expired

The are patch created for BIRD 1.3.4 and 1.3.6, but it would be good to
have this in upstream software, without rebuilding and patching.

as I understand it, no functionality should be affected by these
changes, this is only a visual update for cli.

Old patches describes at pages:
https://marc.info/?l=bird-users&m=132155489919052&w=2
http://trubka.network.cz/pipermail/bird-users/attachments/20120228/a1499be7/attachment-0001.diff
https://bird-users.network.narkive.com/Px6EH3yl/bird-1-3-6-show-bgp-summary-command