MAINTAINERS: add co-maintainer and reviewer for SLAB ALLOCATOR

Promote Harry Yoo from reviewer to maintainer.  Harry's been involved in
slab development for multiple years now and doing a great job.

Add Hao Li as a new reviewer.  Hao has been doing very useful reviews for
a while now, so make it official and ensure the Cc's.

Link: https://lkml.kernel.org/r/20260302101345.36713-2-vbabka@kernel.org


Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Harry Yoo <harry.yoo@oracle.com>
Acked-by: Hao Li <hao.li@linux.dev>
Acked-by: SeongJae Park <sj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>