Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r257531:

Do not exit with error status after printing data for perftest.

Sponsored by: Intel

MFC r256152:

Extend some 32-bit fields and variables to 64-bit to prevent overflow
when calculating data in nvmecontrol perftest.

Sponsored by: Intel

MFC r253109, r253279:

r253109:
Incorporate feedback from bde@ based on r252672 changes:

* Use 0/1 instead of sysexits. Man pages are confusing on this topic,
but 0/1 is sufficient for nvmecontrol.
* Use err function family where possible instead of fprintf/exit.
* Fix some typing errors.
* Clean up some error message inconsistencies.

r253279:
%d should be used for printing int32_t instead of %zd.

clang does not complain about this - only gcc.

Incorporated r253279 prior to MFC timeout because it is required for gcc
builds.

Approved by: re (kib)

MFC r252267:

Break out code related to the perftest command into a separate file.

Sponsored by: Intel

Break out code related to the perftest command into a separate file.

Sponsored by: Intel
MFC after: 3 days