sched_ext: Count SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE in the right spot

sched_ext: Count SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE in the right spot

SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE wasn't quite right in two aspects:

- It counted both migration disabled and offline events.

- It didn't count events from scx_bpf_dsq_move() path.

Fix it by moving the counting into task_can_run_on_remote_rq() which is
shared by both paths and can distinguish the different rejection conditions.
The argument @trigger_error is renamed to @enforce as it now does more than
just triggering error.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Changwoo Min <changwoo@igalia.com>