BLE: Deprecate GapEvent
BLE: Deprecate GapEvent

This class and its components are not used by BLE API and never been used in the
last two years.

This patch deprecate all the components in GapEvent.h and exclude its definitions
from the documentation process.

kjbracey-arm/mbed,betzw/mbed-os,infinnovation/mbed-os,andcor02/mbed-os,Archcady/mbed-os,betzw/mbed-os,CalSol/mbed,infinnovation/mbed-os,ryankurte/mbed-os,andcor02/mbed-os,Archcady/mbed-os,karsev/mbed-os,ryankurte/mbed-os,mbedmicro/mbed,betzw/mbed-os,Archcady/mbed-os,andcor02/mbed-os,c1728p9/mbed-os,kjbracey-arm/mbed,karsev/mbed-os,kjbracey-arm/mbed,c1728p9/mbed-os,c1728p9/mbed-os,mbedmicro/mbed,mazimkhan/mbed-os,c1728p9/mbed-os,mazimkhan/mbed-os,mazimkhan/mbed-os,ryankurte/mbed-os,karsev/mbed-os,betzw/mbed-os,Archcady/mbed-os,andcor02/mbed-os,ryankurte/mbed-os,c1728p9/mbed-os,infinnovation/mbed-os,infinnovation/mbed-os,CalSol/mbed,CalSol/mbed,mazimkhan/mbed-os,CalSol/mbed,karsev/mbed-os,infinnovation/mbed-os,mbedmicro/mbed,infinnovation/mbed-os,karsev/mbed-os,CalSol/mbed,mbedmicro/mbed,andcor02/mbed-os,Archcady/mbed-os,Archcady/mbed-os,mbedmicro/mbed,ryankurte/mbed-os,mazimkhan/mbed-os,betzw/mbed-os,betzw/mbed-os,ryankurte/mbed-os,karsev/mbed-os,mazimkhan/mbed-os,CalSol/mbed,c1728p9/mbed-os,kjbracey-arm/mbed,andcor02/mbed-os