Support SOCK_STREAM for bridge between system and app

Previously AppFuse use SOCK_SEQPACKET for sockets communicating system
and app. However SOCK_SEQPACKET requires the buffer of message size in
the kernel and sometimes failed to write with ENOBUF.

The CL updates libappfuse so that it can use SOCK_STREAM instead of
SOCK_SEQPACKET.

Bug: 33279206
Test: libappfuse_test
Change-Id: I622ada9ac1d71d0c57b6cfff0904c7829cea7995