Update port2alias to work for multi-asic systems.

[abdosi]

What I did

Basically port2alias Cli became broken on multi-asic platforms after introduction of sonic-net/sonic-buildimage#10960 which removed the initialization of global DB config from portconfig.py (library side) and expects application to do it, but here application side (port2alias) was not updated accordingly.
Microsoft ADO: 27245737

How I did it
Add load_db_config call to port2alias for initialization

How to verify it:

Before fix

admin@svcstr2-xxxx-lc3-1:/usr/local/bin$ show interface status | port2alias
Traceback (most recent call last):
  File "/usr/local/bin/port2alias", line 60, in <module>
    main()
  File "/usr/local/bin/port2alias", line 54, in main
    (ports_ns, _, _) = get_port_config(hwsku=hwsku, platform=platform, asic_name=ns)
  File "/usr/local/lib/python3.9/dist-packages/portconfig.py", line 172, in get_port_config
    config_db = db_connect_configdb(asic_name)
  File "/usr/local/lib/python3.9/dist-packages/portconfig.py", line 75, in db_connect_configdb
    config_db = swsscommon.ConfigDBConnector(use_unix_socket_path=True, namespace=namespace)
  File "/usr/lib/python3/dist-packages/swsscommon/swsscommon.py", line 2337, in __init__
    super(ConfigDBConnector, self).__init__(use_unix_socket_path = use_unix_socket_path, namespace = namespace)
  File "/usr/lib/python3/dist-packages/swsscommon/swsscommon.py", line 1966, in __init__
    for db_name in self.get_db_list():
  File "/usr/lib/python3/dist-packages/swsscommon/swsscommon.py", line 1902, in get_db_list
    return _swsscommon.SonicV2Connector_Native_get_db_list(self)
RuntimeError: :- validateNamespace: Initialize global DB config using API SonicDBConfig::initializeGlobalConfig

After fix:

admin@svcstr2-xxxx-lc3-1:/usr/local/bin$ show interface status | port2alias
      Interface                  Lanes    Speed    MTU    FEC        Alias             Vlan    Oper    Admin             Type    Asym PFC
---------------  ---------------------  -------  -----  -----  -----------  ---------------  ------  -------  ---------------  ----------
      Eth0/2/0/0    1288,1289,1290,1291     100G   9100     rs   Eth0/2/0/0  PortChannel1049      up       up  QSFP28 or later         off
      Eth0/2/0/1    1280,1281,1282,1283     100G   9100     rs   Eth0/2/0/1  PortChannel1049      up       up  QSFP28 or later         off
     Eth0/2/0/2    1032,1033,1034,1035     100G   9100     rs   Eth0/2/0/2  PortChannel1050      up       up  QSFP28 or later         off
     Eth0/2/0/3    1024,1025,1026,1027     100G   9100     rs   Eth0/2/0/3  PortChannel1050      up       up  QSFP28 or later         off
     Eth0/2/0/4        776,777,778,779     100G   9100     rs   Eth0/2/0/4  PortChannel1051      up       up  QSFP28 or later         off
     Eth0/2/0/5        768,769,770,771     100G   9100     rs   Eth0/2/0/5  PortChannel1051      up       up  QSFP28 or later         off
     Eth0/2/0/6        520,521,522,523     100G   9100     rs   Eth0/2/0/6  PortChannel1052      up       up  QSFP28 or later         off

[mssonicbld]

Cherry-pick PR to 202305: #3223

[mssonicbld]

Cherry-pick PR to 202311: #3231