Fix syncing back to at mode after ppp disconnect.
Fix AT_CellularContext flags and states to allow new connect after disconnect.
Fix that state machine is not reseted in disconnect is it's running (might be
running because of another context or new connect already started).
Information removed from the cellular subsystem trace log:
* SIM pin
* APN username and password
Added get_debug() to ATHandler.h to get the current trace state in order
to support suspend/resume of trace output.
Change usage of AT_CellularContext::stack_type_supported to
AT_CellularBase::get_property. This way we can rid of
targets overriding stack_type_supported and delete
unnecessary classes and simplify new targets.
Moved methods to classes CellularDevice and CellularInformation.
SIM interface was removed to simplify cellular usage and
methods better suite new classes.
Updated greentea and unit tests.
Add override for the virtual method get_connection_status() inherited
from NetworkInterface. The method in the base class returns
NSAPI_STATUS_ERROR_UNSUPPORTED. The CellularContext has the member
_connection_status, which means that we could return this.
Updated cellular debug trace prints:
- Removed unnecessary prints.
- Tracing more in DEBUG level.
- Read/write bytes not printed on big packets.
- Signal quality (RSSI) traced to log network problems.
- Dismissed AT data is traced.
- Modem type and firmware version are traced.
Network registration returns NotRegistered instead of StatusNotAvailable,
because that's not in 3GPP TS 27.007.