Set TCP maximum segment size to minimum
Previously the socket code would set the TCP maximum segment size to minimum value to prevent IP fragmentation for TCP. This was not yet implemented for the network manager.
Implement network manager functions to set use minimum MTU socket option and set TCP_MAXSEG socket option and use those to clamp the TCP maximum segment size for TCP, TCPDNS and TLSDNS layers in the network manager.
Closes #2201 (closed)
Edited by Ondřej Surý