os-build: enable CONFIG_SCHED_CLASS_EXT for RHEL
<span class="gl-align-middle -gl-mr-2 has-tooltip" title="The source project is a fork"><svg class="s12 gl-ml-1 has-tooltip" data-testid="fork-icon"><use href="/assets/icons-41229992eca580608aadaaa9b83b717650b2863442574d0ebb87f859c42a3b6c.svg#fork"></use></svg></span> prauld/kernel-ark:enable_scx into os-build
Enable sched_ext for RHEL. Since it's enabled for fedora as
well move the config to common. Remove pending-rhel file.
Signed-off-by: Phil Auld pauld@redhat.com