purism-librem5: Enable quick resume support

Hello, I would like to get quick resume support working for the Librem 5. Much like the PinePhone, this allows for the modem to be available immediately out of suspend, alleviating the potential for missed calls if ModemManager takes too long to pick the modem back up.

To do this, the device package for the Librem 5 has been changed to add a modemmanager configuration file, as was done in device-pine64-pinephone, this simply adds --test-quick-suspend-resume to ModemManager's arguments.

In addition, a patch to ModemManager is necessary. Without this patch, SMS will not be received on resume due to differences between the EG25-G (PinePhone) and the BM818 (Librem 5). More details are available in Purism's repository.

That patch has been merged into upstream ModemManager here, but is not yet part of a stable release. I will see if Alpine is willing to accept this patch first, but I've added a commit anyway to package ModemManager in temp.

I've been using this today with many sleep/wake cycles and it seems to be functioning as expected. I'll be daily driving with these patches, and suspend enabled, so I should be able to spot any problems.

This patch does seem to modify how AT fallback works for the PinePhone/Pro (and therefore their quick resume support), so it's likely worth testing that before packaging this, which I can help with if it's decided this approach makes sense.

This is my first MR, so please let me know if I could've done something better, or if I've done something here that doesn't make sense.

Thank you.