Accessor functions for SoftDevice advertising handle

-- Added accessor functions to the Nordic version of the BLEManagerImpl class that allow the
application to get and set the SoftDevice BLE advertising handle.

Author: Jay Logue

src/adaptations/device-layer/include/Weave/DeviceLayer/nRF5/BLEManagerImpl.h

@@ -48,6 +48,15 @@ class BLEManagerImpl final
     // the implementation methods provided by this class.
     friend BLEManager;
 
+public:
+
+    // ===== Platform-specific members available for use by the application.
+
+    uint8_t GetAdvertisingHandle(void);
+    void SetAdvertisingHandle(uint8_t handle);
+
+private:
+
     // ===== Members that implement the BLEManager internal interface.
 
     WEAVE_ERROR _Init(void);
@@ -155,6 +164,16 @@ inline BLEManagerImpl & BLEMgrImpl(void)
     return BLEManagerImpl::sInstance;
 }
 
+inline uint8_t BLEManagerImpl::GetAdvertisingHandle(void)
+{
+    return mAdvHandle;
+}
+
+inline void BLEManagerImpl::SetAdvertisingHandle(uint8_t handle)
+{
+    mAdvHandle = handle;
+}
+
 inline ::nl::Ble::BleLayer * BLEManagerImpl::_GetBleLayer() const
 {
     return (BleLayer *)(this);