1. Added new module parameter zfs_dio_enabled which allows for all reads
and writes to pass through the ARC. This module parameter can be set
to 0 by default in OpenZFS 2.3 release if necessary.
2. Updated ZTS direct tests to account for the new zfs_dio_enabled
module parameter.
3. Updated libzfs.abi to account for changes.
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>