MFC r336353, r336358-r336359, r336414: One big config(8) no-op

r336353:
config(8): Bump major version after r335998

config-generated hints.c/env.c from r335998 and later are incompatible with
earlier kernels due to no longer setting envmode/hintmode. A minor bump for
this is insufficient, as matching major version with a later minor version
is still viewed as backwards-compatible.

This was an MI kernel change, soo all VERSREQ's are bumped.

r336358:
Partially revert r336353: sys/conf/* %VERSREQ bumps

The changes made in r335998 don't strictly require a newer config(8),
though it is advised. The %VERSREQ bumps were premature.

r336359:
Revert 336358 and step away fron machine for the day...

VERSREQ < 7.+ physically will not work with new config(8) due to major bump,
which is why I bumped it in the first place... Back to the original version

r336414:
Revert r336353 completely based on protest; compatibility shims incoming