Expose service changed event to application (1/3)

1. Add onServiceChanged() into IBluetoothGattCallback (AIDL)
2. Define tBTA_GATTC_SERVICE_CHANGED data type
3. Modify the event caller in bta_gatt_act.cc by using new data type
4. Modify the related usages for BTA_GATTC_SRVC_CHG_EVT
5. Handle BTA_GATTC_SRVC_CHG_EVT in btif_gatt_client.cc
6. Add service_change_cb into btgatt_client_callbacks_t
7. Modify the related usages for btgatt_client_callbacks_t

Bug: 154056389
Tag: #feature
Test: test service changed scenario
Change-Id: Ib5f5dac52973e39b22c9e66ee08030d8db768624