[$] Eliminating indirect calls for security modules

Like many kernel subsystems, the Linux security module (LSM) subsystemmakes extensive use of indirect function calls. Those calls, however, areincreasingly problematic, and the pressure to remove them has been growing. The good news is that there is a patchseries from KP Singh that accomplishes that goal. Its progress intothe mainline has been slow - this change was first proposedby Brendan Jackman and Paul Renauld in 2020 - and this work has been caughtup in some wider controversies along the way, but it should be close tobeing ready.