Consolidate connection attempt timeout values

Each different plugin or protocol has a different connection attempt value. E.g. QMI and MBIM both use 60s max for the connection attempt, while the u-blox plugin has up to 180s for ECM based connection setups.

We should have a common timeout value applicable to all, because under low signal quality conditions, the modem may really take a long time to reply, even more than those 60s used as default in QMI or MBIM.

I'd suggest to use up to 180s for the connection attempt and 120s for the clean disconnection attempt, same as in qmicli since libqmi!168 (merged)