unit/test-gatt: Add /TP/GAW/CL/BI-18-C/auto test
unit/test-gatt: Add /TP/GAW/CL/BI-18-C/auto test

/TP/GAW/CL/BI-18-C/auto is similar to /TP/GAW/CL/BI-18-C but
automatically elevates the security level and retry.

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