Bluetooth: Mesh: Transport SAR Configuration

Add support for:
- SAR Configuration Client and Server models
- Transport SAR configuration states
- Using SAR Transmitter/Receiver states in segmentation
and reassembly process.

Bsim tests fixes:
- Fix failing replay attack test. The replay attack test doesn't
consider retransmission attempts at the transport layer. When
retransmission happens, SeqNums get increased and the test logic
doesn't work anymore. The simplest fix would be to disable
retransmissions at the transport layer.
- Add device synchronization API to synchronize transport va test.
Device configuration may take different time on transmitter and
receiver. Add synchronisation barrier between devices.
- Fix msg_frnd test. Timing in transport sar behavior has been
changed, which affected test_friend_msg test. Now acknowledgments
are sent much faster and this needs to be considered in the test.
- Fix unicast_low_lat test. Increase number of retransmission
attempts when long segmented message is sent.
- Reduce timeout in kr_old_key test.
- Relax SAR RX state configuration in DFU and BLOB tests.

Co-authored-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>
Co-authored-by: Anders Storrø <anders.storro@nordicsemi.no>
Co-authored-by: Ingar Kulbrandstad <ingar.kulbrandstad@nordicsemi.no>
Signed-off-by: Michał Narajowski <michal.narajowski@codecoup.pl>
Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>