This adds another helper macro called BT_GATT_CCC_MANAGED which can be
used to set 2 new callbacks:
- cfg_write: Which application can set if it wants to manage writes to
CCC configuration.
- cfg_match: Which application can set if it wants to manage matching
CCC configuration when notifying/indicating.
BT_GATT_CCC_MANAGED retains the ability of saving peer configuration
on storage making it useful for clients which are only interrested in
managing the CCC configuration but not the storage itself.
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>