Add Connect() method to console DBUS object

Added new poller and consumer for the console DBUS data.

Note: We initially developed SocketName attribute but it is now
      deprecated/removed.

The tree of default object:
$ busctl tree xyz.openbmc_project.Console.default
`-/xyz
  `-/xyz/openbmc_project
    `-/xyz/openbmc_project/console
      `-/xyz/openbmc_project/console/default

The introspect of default console:
$ busctl introspect xyz.openbmc_project.Console.default /xyz/openbmc_project/console/default
NAME                                TYPE      SIGNATURE RESULT/VALUE FLAGS
org.freedesktop.DBus.Introspectable interface -         -            -
.Introspect                         method    -         s            -
org.freedesktop.DBus.Peer           interface -         -            -
.GetMachineId                       method    -         s            -
.Ping                               method    -         -            -
org.freedesktop.DBus.Properties     interface -         -            -
.Get                                method    ss        v            -
.GetAll                             method    s         a{sv}        -
.Set                                method    ssv       -            -
.PropertiesChanged                  signal    sa{sv}as  -            -
xyz.openbmc_project.Console.Access  interface -         -            -
.Connect                            method    -         h            -
xyz.openbmc_project.console         interface -         -            -
.setBaudRate                        method    u         x            -
.baudrate                           property  u         0            -

Tested:
  Performed integration testing with bmcweb.

Change-Id: I2444b1083cf26536f43c6f6b4b0857a2921c4f78
Signed-off-by: Ninad Palsule <ninadpalsule@us.ibm.com>
diff --git a/console-server.h b/console-server.h
index 5343af8..47302dc 100644
--- a/console-server.h
+++ b/console-server.h
@@ -230,6 +230,9 @@
 void dbus_init(struct console *console,
 	       struct config *config __attribute__((unused)));
 
+/* socket-handler API */
+int dbus_create_socket_consumer(struct console *console);
+
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
 
 #ifndef offsetof