Let's not have sim pin handling in multiple places

We have sim handling via gnome-settings-daemon (although we don't ship it on the devkit) so I wonder if it's the right approach to handle sim handling again in chatty? @mohammed.sadiq is working on similar things in gnome-control-center / gnome-settings-daemon. We don't want to store the sim in unlocked memory (https://source.puri.sm/Librem5/gnome-settings-daemon/issues/2) but use gnome-keyring for that.

Also this might waste precious retries when the user changes it's pin via g-c-c- (which can update the pin stored in the keyring)

cc: @bob.ham (since calls needs the sim unlocked as well)

i've moved the comment from !2 (comment 43133) over here.