futex: Rebase futex code to v6.8
JIRA: https://issues.redhat.com/browse/RHEL-28616
MR: !3827
This MR rebases the RHEL9 futex code base to align to the v6.8 upstream kernel to gain access to new futex syscalls and functionality that are likely needed by userspace applications and other kernel subsystems.
It also includes the reverting of some linux-rt-devel specific rt-mutex and scheduler patches and replacing them with upstream linux equivalents. It also includes some unrelated syscall patches. These are all done to ease the current and future backporting effort.
Signed-off-by: Waiman Long longman@redhat.com
Edited by Waiman Long