scsi: scsi_debug: Add write support with block lengths and 4 bytes of data

scsi: scsi_debug: Add write support with block lengths and 4 bytes of data

The tape is implemented as fixed number (10 000) of 8-byte units.  The
first four bytes of a unit contains the type of the unit (data block,
filemark or end-of-data mark). If the units is a data block, the first four
bytes contain the block length and the remaining four bytes the first bytes
of written data. This allows the user to use tags to see that the read
block is what it was supposed to be.

The tape can contain two partitions. Initially it is formatted as one
partition consisting of all 10 000 units.

This patch adds the WRITE(6) command for tapes and the WRITE FILEMARKS (6)
command. The REWIND command is updated.

Signed-off-by: Kai Mäkisara <Kai.Makisara@kolumbus.fi>
Link: https://lore.kernel.org/r/20250213092636.2510-4-Kai.Makisara@kolumbus.fi
Reviewed-by: John Meneghini <jmeneghi@redhat.com>
Tested-by: John Meneghini <jmeneghi@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>