tests: Bluetooth: df: Add tests for use of CTE in per adv chains

Bluetooth host may request to send more than one CTE in
connectionless mode. That is relized by periodic advertising
chained PDUs.
To check correctness of implementation of such functionality
new unit tests were added.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>