Previously, we had a sort of double reference count with refcount being
used to track how many waits were holding a reference and pending being
used to track whether or not it was in the pending list. This meant
that the unref operation actually had to look at both refcount and
pending in order to determine if it could free the time point. This is
way too confusing. Instead, we should just always take a reference
while we're pending.
This also simplifies the over-all interface because there's no longer a
difference between free and release. `struct vk_sync_timeline_point` is
now just a reference-counted API.
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35921>
(cherry picked from commit 088a979e79)