oniro-image-common.inc/networkmanager: Add modem/usbmodem MACHINE_FEATURE

Enable a modem/usbmodem MACHINE_FEATURE to install the needed packages
for NetworkManager and ModemManager in the image. Also enabling the
ModemManager PACKAGECONFIG for NetworkManager to build the needed support.

Fixes: eclipse/oniro-core/oniro#60



Signed-off-by: Stefan Schmidt <stefan.schmidt@huawei.com>