Bluetooth: host: Enable CONFIG_BT_SETTINGS_CCC_STORE_ON_WRITE

Storing CCC right after it's written reduces risk of inconsistency
of CCC values between bonded peers. The option should be enabled by
default. The developer could explicitly disable it to reduce memory
usage. After disabling the option explicitly, the developer is
aware of related potential issues.

Fixes: #40758

Signed-off-by: Marek Pieta <Marek.Pieta@nordicsemi.no>