[$] Eliminating indirect calls for security modules

Like many kernel subsystems, the Linux security module (LSM) subsystem
makes extensive use of indirect function calls. Those calls, however, are
increasingly problematic, and the pressure to remove them has been growing.
The good news is that there is a patch
series from KP Singh that accomplishes that goal. Its progress into
the mainline has been slow — this change was first proposed
by Brendan Jackman and Paul Renauld in 2020 — and this work has been caught
up in some wider controversies along the way, but it should be close to
being ready.