api,modem: new 'GetCellInfo()' method

This new method allows querying the modem for information about the
current serving cell(s) as well as any other neighboring cell that may
be found.

The information for the cells is given in an array of dictionaries,
where each element of the dictionary is a new dictionary itself.

Each cell type has a different set of properties that may be given in
the dictionary, and some of those properties in each type are also
applicable under certain conditions (e.g. only applicable to the cell
if it's a 'serving' cell instead of 'neighboring').

The API documentation explains in detail what is expected in each
case.

docs/reference/api/ModemManager-sections.txt

@@ -63,6 +63,7 @@ MMSmsCdmaServiceCategory
 MMSimType
 MMSimEsimStatus
 MMSimRemovability
+MMCellType
 </SECTION>
 
 <SECTION>

docs/reference/libmm-glib/libmm-glib-sections.txt

@@ -1791,6 +1791,7 @@ mm_oma_session_state_failed_reason_get_string
 mm_call_direction_get_string
 mm_call_state_get_string
 mm_call_state_reason_get_string
+mm_cell_type_get_string
 <SUBSECTION Private>
 mm_modem_capability_get_string
 mm_modem_lock_build_string_from_mask
@@ -1845,6 +1846,7 @@ mm_call_direction_build_string_from_mask
 mm_call_state_build_string_from_mask
 mm_call_state_reason_build_string_from_mask
 mm_modem_firmware_update_method_get_string
+mm_cell_type_build_string_from_mask
 <SUBSECTION Standard>
 MM_TYPE_BEARER_TYPE
 MM_TYPE_BEARER_IP_FAMILY
@@ -1899,6 +1901,7 @@ MM_TYPE_CALL_DIRECTION
 MM_TYPE_CALL_STATE
 MM_TYPE_CALL_STATE_REASON
 MM_TYPE_MODEM_FIRMWARE_UPDATE_METHOD
+MM_TYPE_CELL_TYPE
 mm_bearer_type_get_type
 mm_bearer_ip_family_get_type
 mm_bearer_ip_method_get_type
@@ -1952,6 +1955,7 @@ mm_call_direction_get_type
 mm_call_state_get_type
 mm_call_state_reason_get_type
 mm_modem_firmware_update_method_get_type
+mm_cell_type_get_type
 </SECTION>
 
 <SECTION>
@@ -2563,6 +2567,9 @@ mm_gdbus_modem_call_set_primary_sim_slot_sync
 mm_gdbus_modem_call_command
 mm_gdbus_modem_call_command_finish
 mm_gdbus_modem_call_command_sync
+mm_gdbus_modem_call_get_cell_info
+mm_gdbus_modem_call_get_cell_info_finish
+mm_gdbus_modem_call_get_cell_info_sync
 <SUBSECTION Private>
 mm_gdbus_modem_set_access_technologies
 mm_gdbus_modem_set_bearers
@@ -2612,6 +2619,7 @@ mm_gdbus_modem_complete_set_current_modes
 mm_gdbus_modem_complete_set_current_bands
 mm_gdbus_modem_complete_set_current_capabilities
 mm_gdbus_modem_complete_set_primary_sim_slot
+mm_gdbus_modem_complete_get_cell_info
 mm_gdbus_modem_interface_info
 mm_gdbus_modem_override_properties
 <SUBSECTION Standard>