o Exercise bounds checking when sending large set of file descriptors,
that can't fit into single control mbuf.
o Exercise resource limits checks when receiving a large sets.
o Check that socket isn't left in a completely stuck state when we can't
receive SCM_RIGHTS due to limits. Current SOCK_STREAM socket would
free the control, but leave the data in. This seems to be a legit
behavior for a stream socket, as we don't want holes in the data.
PR: 239250
Reviewed by: markj
Differential revision: https://reviews.freebsd.org/D35315
23402c83f4