selftests: Use ktap helpers for runner.sh

selftests: Use ktap helpers for runner.sh

Instead of manually writing ktap messages, we should use the formal
ktap helpers in runner.sh. Brendan did some work in commit d9e6269e3303
("selftests/run_kselftest.sh: exit with error if tests fail") to make
run_kselftest.sh exit with the correct return value. However, the output
does not include the total results, such as how many tests passed or failed.

Let’s convert all manually printed messages in runner.sh to use the
formal ktap helpers. Here are what I changed:

  1. Move TAP header from runner.sh to run_kselftest.sh, since
     run_kselftest.sh is the only caller of run_many().
  2. In run_kselftest.sh, call run_many() in main process to count the
     pass/fail numbers.
  3. In run_kselftest.sh, do not generate kselftest_failures_file. Just
     use ktap_print_totals to report the result.
  4. In runner.sh run_one(), get the return value and use ktap helpers for
     all pass/fail reporting. This allows counting pass/fail numbers in the
     main process.
  5. In runner.sh run_in_netns(), also return the correct rc, so we can
     count results during wait.

After the change, the printed result looks like:

  not ok 4 4 selftests: clone3: clone3_cap_checkpoint_restore # exit=1
  # Totals: pass:3 fail:1 xfail:0 xpass:0 skip:0 error:0

  ]# echo $?
  1

Fixed change log commit description errors and long lines:
Shuah Khan <skhan@linuxfoundation.org>

Tested-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Link: https://lore.kernel.org/r/20260225010833.11301-1-liuhangbin@gmail.com
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>