Fix handling of optional fields in get_bgp_peer function

[matofeder]

What I did

This commit fixes an issue in get_bgp_peer function where local_addr and name were treated as mandatory. However, local_addr and name fields are not required in BGP neighbor configuration.

How I did it

The local_addr and name fields are no longer mandatory in the get_bgp_peer function.

How to verify it

Apply BGP neighbor configuration like below (utilizing BGP_PEER_GROUP), where fields such as local_addr or name are omitted:

{ 
    "BGP_GLOBALS": {
        "default": {
            "local_asn": "65001",
            "log_nbr_state_changes": "true",
            "router_id": "10.0.0.1"
        }
    },
   "BGP_PEER_GROUP": {
        "default|core": {
          "peer_group_name": "core",
          "admin_status": "true",
          "asn": "65002",
          "peer_type": "external"
        }
     },
    "BGP_NEIGHBOR": {
        "default|Ethernet4": {
            "peer_group_name": "core"
        }
    },
    "BGP_NEIGHBOR_AF": {
        "default|core|ipv4_unicast": {
            "admin_status": "true",
            "route_map_in": [
                "ALLOW"
            ],
            "route_map_out": [
                "ALLOW"
            ]
        }
    },
    "ROUTE_MAP": {
        "ALLOW|1": {
            "route_operation": "permit"
        }
    }
}

Previous command output (if the output of a command-line utility has changed)

root@sw1:~# show ip interfaces 
Traceback (most recent call last):
  File "/usr/local/bin/ipintutil", line 280, in <module>
    main()
  File "/usr/local/bin/ipintutil", line 273, in main
    ip_intfs = get_ip_intfs(af, namespace, display)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/bin/ipintutil", line 236, in get_ip_intfs
    ip_intfs_in_ns = get_ip_intfs_in_namespace(af, namespace, display)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/bin/ipintutil", line 149, in get_ip_intfs_in_namespace
    bgp_peer = get_bgp_peer()
               ^^^^^^^^^^^^^^
  File "/usr/local/bin/ipintutil", line 51, in get_bgp_peer
    local_addr = data[neighbor_ip]['local_addr']
                 ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
KeyError: 'local_addr'

New command output (if the output of a command-line utility has changed)

root@sw1:~# show ip interfaces 
Interface    Master    IPv4 address/mask    Admin/Oper    BGP Neighbor    Neighbor IP
-----------  --------  -------------------  ------------  --------------  -------------
Ethernet4              1.1.1.0/31           up/up         N/A             N/A

Fixes #19930