MAINTAINERS: update page allocator section

MAINTAINERS: update page allocator section

Make Vlastimil maintainer of this section (with thanks to Vlastimil for
agreeing to this!) and add page isolation files for which this section
seem most appropriate.

We may wish to, in future, refactor/rename some of these files to more
logically fit what is actually being performed, but for the time being
this seems the most sensible place.

Additionally, fix the alphabetical ordering of files.

Link: https://lkml.kernel.org/r/20250512144603.90379-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>