shared/gatt: Discover secondary services
shared/gatt: Discover secondary services

Add searching of secondary services in gatt-client.

pstglia/external-bluetooth-bluez,ComputeCycles/bluez,pkarasev3/bluez,pkarasev3/bluez,mapfau/bluez,silent-snowman/bluez,mapfau/bluez,mapfau/bluez,ComputeCycles/bluez,silent-snowman/bluez,mapfau/bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,silent-snowman/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,silent-snowman/bluez,ComputeCycles/bluez