Draft: api,modem: new 'IgnoredPorts' property

External programs like fwupd rely on ModemManager's port probing results to discover a Modem's ports. Currently only if MM_PLUGIN_REQUIRED_QCDM is set, the QCDM port will be probed. If the port is flagged as QCDM in the Udev rules and only MM_PLUGIN_ALLOWED_QCDM is set, the port will be set to ignored without probing and therefore not visible as QCDM via mm_modem_get_ports().

Removes the use of MM_MODEM_PORT_TYPE_IGNORED and set the ignored property seperately. All ports with the ignored property will be exposed as a list of 'IgnoredPorts'.