Revert "Work around the case where hisory buffer is larger than HIS_BUF_LEN (128K)."

This reverts commit b447e0422302d17b8d84a238afe594ac78a93a5b.
Take into account when zpool history block grows exceeding 128KB in zpool(8)
and zdb(8) by growing the buffer on demand with a cap of 1GB (specified in
spa_history_create_obj()).

PR:		bin/186574
Submitted by:	Andrew Childs <lorne cons org nz> (with changes)
MFC after:	2 weeks

(cherry picked from commit 78e547c5404320fbd04ad333c9f9691a30b0e86e)

Ticket: #4736