SMS support for the mobile version of Sculpt OS

[nfeske]

Sculpt OS on the PinePhone needs to support the reception and sending of SMS messages.

The modem_pinephone.run script provided by the genode-allwinner repository already allows for the sending and receiving of text messages by issuing AT commands in the interactive mode. However, to accommodate Sculpt OS, the modem driver needs to be extended with the ability to export the available messages (as XML), delete messages from the SIM card, and to send messages.

The article https://lupyuen.github.io/articles/lte2 provides many useful clues to be considered while implementing this feature. One particularly interesting insight is the preference of the PDU encoding over text-mode messages.

[nfeske]

Commit nfeske@d1408c2 implements a parser for PDUs of type "SMS-DELIVER" as obtained via the AT+CMGL AT command.