Merge branch 'af_unix-gc-cleanup-and-optimisation'

Kuniyuki Iwashima says:

====================
af_unix: GC cleanup and optimisation.

Currently, AF_UNIX GC is triggered from close() and sendmsg()
based on the number of inflight AF_UNIX sockets.

This is because the old GC implementation had no idea of the
shape of the graph formed by SCM_RIGHTS references.

The new GC knows whether cyclic references (could) exist.

This series refines such conditions not to trigger GC unless
really needed.
====================

Link: https://patch.msgid.link/20251115020935.2643121-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>