DLPX-95109 could not find 'spa_t *' when running sdb -e 'spa' on dump

[mmaybee]

Problem

We sometimes see that the the spa command works, but often not. After
some investigation it became clear that the issue here is that required
pages were being excluded from the generated dump file (as a result of
the makedumpfile -d flag) that result in drgn ignoring multiple kernel
modules (including the zfs module).

Solution

Trial and error testing revealed that switching from -d 31 (default
setting for makedumpfile that excludes all pages it deems unnecessary
for debugging) to -d 23 (excluding all those pages except the
“user data” pages) results in a dump file that is larger, but also
does not cause drgn to report “Excluded page” errors at startup.
This version of the dump file appears to allow full sdb debugging.

Testing Done

https://selfservice-jenkins.eng-tools-prd.aws.delphixcloud.com/job/appliance-build-orchestrator-pre-push/12045/