integritysetup: support mode=(journal|bitmap|direct)

integritysetup: support mode=(journal|bitmap|direct)

Add a parameter to the integritytab file to set the mode in which to
open the integrity volume. The mode can be journaled (the default),
bitmap without a journal, or direct mode without a journal or a bitmap.

This change removes the `no-journal' option because it is redundant,
being replaced with `mode=direct'.

Supercedes commit bcc1ee56c, from a week ago, which implemented
`no-journal'.

Resolves #27587