dmu_tx_assign: make all VERIFY0 calls use DMU_TX_SUSPEND

This is the cheap way to keep non-user functions working after
break-on-suspend becomes default.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Closes #17355