unit/gatt: Add /TP/GAR/SR/BI-18-C test
unit/gatt: Add /TP/GAR/SR/BI-18-C test

Verify that a Generic Attribute Profile server can detect and reject a
Read Multiple Characteristic Values Request including any non-readable
Characteristic Value and issue a Read Not Permitted Response.

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