selftests/mm: khugepaged: use kselftest framework

selftests/mm: khugepaged: use kselftest framework

Convert khugepaged tests to use kselftest framework for reporting and
tracking successful and failing runs.

The conversion is mostly about replacing printf()/perror() + exit() pairs
with their ksft_ counterparts.

The nice colored success and failure indications are left intact.

Replace the progress report in collapse_compound_extreme() with a single
ksft_print_msg() to avoid headache with formatting and make the test
output more concise.

[rppt@kernel.org: make the output TAP-compatible]
[ziy@nvidia.com: update for "Remove CONFIG_READ_ONLY_THP_FOR_FS and enable file THP for writable files", v6]
  https://lore.kernel.org/20260517135416.1434539-1-ziy@nvidia.com
Link: https://lore.kernel.org/20260511162840.375890-15-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Tested-by: Luiz Capitulino <luizcap@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Donet Tom <donettom@linux.ibm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Li Wang <li.wang@linux.dev>
Cc: Sarthak Sharma <sarthak.sharma@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>