modem-qmi: implement multiparty call functionalities

The following functionalities are implemented:

1. Hold all and accept
2. Hangup all and accept
3. Hangup all
4. Join multiparty
5. Leave multiparty
6. Call transfer - Fails. Maybe this functionality is not available in my network. I don't seen any similar feature in android to try this. Am I missing something?
7. Call waiting setup
8. Call waiting query

Overall, the rest of the functionalities are tested to be working on the outlook, but these might require extensive testing.

Requires libqmi MR to be merged first: libqmi!263 (merged)