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ARROW-14476: [CI] Crossbow should comment cause of failure

This also handles ARROW-14366 by adding a comment if the requesting user is not yet a contributor.

Closes #11571 from jeszyb/arrow-14476

Authored-by: jeszyb <jeszyb@gmail.com>
Signed-off-by: Krisztián Szűcs <szucs.krisztian@gmail.com>