bgpd: Add an ability to filter UPDATEs using neighbor with prefix-list

bgpd: Add an ability to filter UPDATEs using neighbor with prefix-list

Before this patch we didn't have an option to filter debug UPDATE messages
by specifying an arbitrary prefix, prefix-list or so. We had/have only an option
to specify:

```
* debug bgp updates in 10.0.0.1
* debug bgp updates prefix 10.0.1.0/24
```

Now adding:

```
* debug bgp updates <in|out> 10.0.0.1 prefix-list plist
```

CLI output:

```
r2# show debugging
MGMT debugging status:

Zebra debugging status:

BGP debugging status:
  BGP updates debugging is on (inbound) for 192.168.2.6 with prefix-list debug

Staticd debugging status

r2# show running-config | include prefix-list debug
debug bgp updates in 192.168.2.6 prefix-list debug
r2#
```

Logs:

```
BGP: [PCFFM-WMARW] 192.168.2.3(r3) rcvd UPDATE wlen 0 attrlen 28 alen 5
BGP: [PCFFM-WMARW] 192.168.2.3(r3) rcvd UPDATE wlen 0 attrlen 28 alen 4
BGP: [PCFFM-WMARW] 192.168.2.3(r3) rcvd UPDATE wlen 0 attrlen 0 alen 0
BGP: [M59KS-A3ZXZ] bgp_update_receive: rcvd End-of-RIB for IPv4 Unicast from 192.168.2.3 in vrf default
BGP: [PCFFM-WMARW] 192.168.2.4(r4) rcvd UPDATE wlen 0 attrlen 28 alen 5
BGP: [PCFFM-WMARW] 192.168.2.4(r4) rcvd UPDATE wlen 0 attrlen 28 alen 4
BGP: [PCFFM-WMARW] 192.168.2.4(r4) rcvd UPDATE wlen 0 attrlen 0 alen 0
BGP: [M59KS-A3ZXZ] bgp_update_receive: rcvd End-of-RIB for IPv4 Unicast from 192.168.2.4 in vrf default
BGP: [PCFFM-WMARW] 192.168.1.1(r1) rcvd UPDATE wlen 0 attrlen 29 alen 5
BGP: [PCFFM-WMARW] 192.168.2.6(r6) rcvd UPDATE wlen 0 attrlen 28 alen 5
BGP: [XXWBM-V772F] 192.168.2.6(r6) rcvd UPDATE w/ attr: nexthop 192.168.2.6, origin ?, metric 0, path 65006
BGP: [YCKEM-GB33T] 192.168.2.6(r6) rcvd 172.16.16.254/32 IPv4 unicast <<<<<<<<<<<<
BGP: [PCFFM-WMARW] 192.168.2.6(r6) rcvd UPDATE wlen 0 attrlen 28 alen 4
BGP: [PCFFM-WMARW] 192.168.2.6(r6) rcvd UPDATE wlen 0 attrlen 0 alen 0
BGP: [M59KS-A3ZXZ] bgp_update_receive: rcvd End-of-RIB for IPv4 Unicast from 192.168.2.6 in vrf default
BGP: [PCFFM-WMARW] 192.168.2.5(r5) rcvd UPDATE wlen 0 attrlen 28 alen 5
BGP: [PCFFM-WMARW] 192.168.2.5(r5) rcvd UPDATE wlen 0 attrlen 28 alen 4
BGP: [PCFFM-WMARW] 192.168.2.5(r5) rcvd UPDATE wlen 0 attrlen 0 alen 0
BGP: [M59KS-A3ZXZ] bgp_update_receive: rcvd End-of-RIB for IPv4 Unicast from 192.168.2.5 in vrf default
BGP: [PCFFM-WMARW] 192.168.1.1(r1) rcvd UPDATE wlen 0 attrlen 29 alen 5
BGP: [PCFFM-WMARW] 192.168.7.7(r7) rcvd UPDATE wlen 0 attrlen 0 alen 0
BGP: [M59KS-A3ZXZ] bgp_update_receive: rcvd End-of-RIB for IPv4 Unicast from 192.168.7.7 in vrf default
```

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>