bgpd: revamp evpn debugs nexthop and l3vni

bgpd: revamp evpn debugs nexthop and l3vni

Add nexthop fied when import/unimport evpn route in vrf,
print bgp vrf instance name which contains "VRF" keyword.

Include pathcount which is list of paths linked to nexthop.

add and delete l3vni to keep symmetric "L3VNI" keyword as
used in other debug statements.

Ticket: #3671288
Testing Done:

2023/12/27 05:10:03.339616 BGP: [HPE1G-3H7F2] ... new pi VRF vrf2
dest 0x55663e8372c0 (l 2) pi 0x55663e8374d0 (l 1, f 0x4010) nh 6.0.0.1

2023/12/27 05:58:56.650116 BGP: [MC0JJ-7ZYQB] ... delete pi VRF vrf2
dest 0x55663e885110 (l 5) pi 0x55663e8851e0 (l 1, f 0x4098) nh 6.0.0.1

2023/12/27 05:10:03.339581 BGP: [P4TBX-3W31N] evpn VRF vrf2 nh
6.0.0.1 rmac 00:02:00:00:00:04 add to zebra

2023/12/27 06:13:12.685906 BGP: [SWSCZ-2Z6M4] evpn vrf VRF vrf1 nh
6.0.0.1 del to zebra

2023/12/27 05:10:03.339603 BGP: [Y2EAK-4N7FV] path 60.1.1.111/32 linked
to VRF vrf2 nh 6.0.0.1 pathcount 0

2023/12/27 05:58:56.650125 BGP: [GVE17-CSNTB] path 81.1.1.0/24 unlinked
from VRF vrf2 nh 6.0.0.1 pathcount 16

2023/12/27 05:08:10.108038 ZEBRA: [Q8ZEK-CT776] Send L3VNI ADD 104001
VRF vrf1 RMAC 00:04:ba:10:10:62 VRR 1c:34:da:19:59:62 local-ip 6.0.0.31
filter none to bgp

2023/12/27 05:08:26.043121 ZEBRA: [R43YF-2MKZ3] Send L3VNI DEL 104001
VRF vrf1 to bgp

Signed-off-by: Chirag Shah <chirag@nvidia.com>