MFC 271381-271382,271385,271463-271466,271485,271506

o Add sysctls to enable/disable potentially dengerous key combinations, like
        reboot/halt/debug.
o Add support for most key combinations supported by syscons(4).
o Some spelling fixes
o Remove stray whitespaces.
o Switch vt(4) to traditional behaviour with copy-paste same as syscons(4) do.
o Fix stray char on paste.
o Fix 'function declaration isn't a prototype' warning.
o vt(4): Enclose vt_mouse_paste() prototype inside #ifndef SC_NO_CUTPASTE/#endif

Approved by:	re (gjb)
Sponsored by:	The FreeBSD Foundation
MFC r271450:
cxgbe(4): knobs to enable/disable PAUSE frame based flow control.

Approved by:	re (glebius)
MFC r271459:

Fix ACL tests to correctly work with ZFS; previous version used wrong
paths.

PR:		191545
Approved by:	re (gjb)
Sponsored by:	The FreeBSD Foundation
MFC r271711:
  Update the bhyve(8) manual to reflect that it is no
  longer considered 'experimental.'

Approved by:	re (delphij)
Sponsored by:	The FreeBSD Foundation
MFC 271482: Add support for adding empty partition entries.

Relnotes:	yes
Approved by:	re@ (gjb)
MFC r271679:

  Merge atse(4) interrupt handling and race condition fixes from
  cheribsd.

  Obtained from:	cheribsd
  Submitted by:		rwatson, emaste
Sponsored by:		DARPA/AFRL
Approved by:		re (delphij)