MFV r258371,r258372: 4101 metaslab_debug should allow for fine-grained control

4101 metaslab_debug should allow for fine-grained control
4102 space_maps should store more information about themselves
4103 space map object blocksize should be increased
4104 ::spa_space no longer works
4105 removing a mirrored log device results in a leaked object
4106 asynchronously load metaslab

illumos/illumos-gate@0713e232b7712cd27d99e1e935ebb8d5de61c57d

Note that some tunables have been removed and some new tunables have
been added.  Of particular note, FreeBSD-only knob
vfs.zfs.space_map_last_hope is removed as it was a nop for some time now
(after one of the previous merges from upstream).

MFC after:	11 days
Sponsored by:	HybridCluster [merge]
jail_v0.ip_number was always in host byte order.  This was handled
in one of the many layers of indirection and shims through stable/7
in jail_handle_ips().  When it was cleaned up and unified through
kern_jail() for 8.x, the byte order swap was lost.

This only matters for ancient binaries that call jail(2) themselves
internally.
Purely cosmetic change: order DT_REL* and DT_RELA* consistently.

From projects/uefi, r246107

Sponsored by:	The FreeBSD Foundation