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 r235911, r235980, r238739, r238740, r238894, r239213, r241488, r241952,
r242173, r242621, r242634, r242638, r242647, r242720, r244418, r244508,
r245891:
Revamp the CAM enclosure services driver.
This updated driver uses an in-kernel daemon to track state changes and
publishes physical path location information for disk elements into the
CAM device database.

Sponsored by: Spectra Logic Corporation
Sponsored by: iXsystems, Inc.

MFprojects/zfsd:
Revamp the CAM enclosure services driver.
This updated driver uses an in-kernel daemon to track state changes and
publishes physical path location information\for disk elements into the
CAM device database.

Sponsored by: Spectra Logic Corporation
Sponsored by: iXsystems, Inc.
Submitted by: gibbs, will, mav