tests: bluetooth: mesh: Test confirm step in DFU with different effects

This commit implements the following tests:
- Test that DFU finishes successfully with all different effects;
- Test that DFU fails at confirm step with all different effects;

Co-authored-by: Krzysztof Kopyściński <krzysztof.kopyscinski@codecoup.pl>
Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>