rtla/tests: Don't rely on matching ^1ALL

rtla/tests: Don't rely on matching ^1ALL

The timerlat "top stop at failed action" test was relying on "ALL" being
printed immediately after the "1" from the threshold action.  Besides being
fragile, this depends on stdbuf behavior, which is easy to miss when
recreating the test outside of the framework for debugging purposes.

Instead, use the expected/unexpected text mechanism from the
corresponding osnoise test.

Signed-off-by: Crystal Wood <crwood@redhat.com>
Link: https://lore.kernel.org/r/20251112152529.956778-2-crwood@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>