MFOpenZFS: Fix zpool history unbounded memory usage

MFOpenZFS: Fix zpool history unbounded memory usage

In original implementation, zpool history will read the whole history
before printing anything, causing memory usage goes unbounded. We fix
this by breaking it into read-print iterations.

Reviewed-by: Tom Caputi <tcaputi@datto.com>
Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@nutanix.com>
Closes #9516

Note, this change changes the libzfs.so ABI by modifying the prototype
of zpool_get_history().  Since libzfs is effectively private to the base
system it is anticipated that this will not be a problem.

PR:		247557
Obtained from:	OpenZFS
Reported and tested by:	Sam Vaughan <samjvaughan@gmail.com>
Discussed with:	freqlabs
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D25745
openzfs/zfs@7125a109dcc55628336ff3f58e59e503f4d7694d