post 5.14 scheduler fixes

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1992256

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1981743

Upstream Status: Linux
Tested: With cki, with assorted scheduler, stress and sanity tests.

Assorted updates from after the 5.14 rebase. This make the core scheduler
code pretty close to 5.15.

Signed-off-by: Phil Auld pauld@redhat.com