mm/damon: rename damos core filter helpers to have word core

mm/damon: rename damos core filter helpers to have word core

Patch series "mm/damon: misc cleanups".

Yet another batch of misc cleanups and refactoring for DAMON code, tests,
and documents.

First two patches (1and 2) rename DAMOS core filters related code for
readability.

Three following patches (3-5) refactor page table walk callback functions
in DAMON, as suggested by Hugh and David, and I promised.

Next two patches (6 and 7) refactor DAMON core layer kunit test and sysfs
interface selftest to be simple and deduplicated.

Final two patches (8 and 9) fix up sphinx and grammatical errors on
documents.

This patch (of 9):

DAMOS filters handled by the core layer are called core filters, while
those handled by the ops layer are called ops filters.  They share the
same type but are managed in different places since core filters are
evaluated before the ops filters.  They also have different helper
functions that depend on their managed places.

The helper functions for ops filters have '_ops_' keyword on their name,
so it is easy to know they are for ops filters.  Meanwhile, the helper
functions for core filters are not having the 'core' keyword on their
name.  This makes it easy to be mistakenly used for ops filters.  Actually
there was such a bug.

To avoid future mistakes from similar confusions, rename DAMOS core
filters helper functions to have a keyword 'core' on their names.

Link: https://lkml.kernel.org/r/20251112154114.66053-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20251112154114.66053-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Bill Wendling <morbo@google.com>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>