cmake: fix warnings, code cleanup

license: update text

mesh: avoid out of bounds reads

mesh: streamline mesh-access-parser uint getter names

mesh: remove num_segments and segmented flag from access message builder

mesh: use single access builder

mesh: use mesh_upper_transport_pdu_t for all access messages, remove mesh_transport_pdu_t

mesh: mesh_message_pdu -> mesh_segmented_pdu

mesh: use mesh_message_t for unsegmented access messages

mesh: expand count_log to count, and period_log to period_s in heartbeat messages of configuration client [a2592]

mesh: add destination field to heartbeat messages of configuration client [a2591]

mesh: implement config client network transmit msgs [a2583]

mesh: implement config client low power node msgs [a2582]

mesh: implement config client heartbeat publication and subscription msgs [a2580, a2581]

mesh: implement config client key refresh msgs [a2579]

mesh: implement config client node reset and friend msgs [a2578,a2584]

mesh: implement sig and vendor model app list

mesh: implement mesh client configuration model appkey bind/unbind messages

mesh: implement mesh client configuration node identity messages

mesh_configuraiton_client: implement netkey and appkey messages

mesh_configuraiton_client: subscription get and list messages

mesh: implement model subscription messages

mesh: fix compile warnings

mesh_configuraiton_client: implement config model publication set/get/status

mesh: add unit test for elements descriptions iterator, add missing getter for CONFIGURATION_COMPOSITION_DATA event, fix offsets in existing getters