update kernel_version() to support printing verbose output for different FreeBSD releases and snapshots.

adding a more detailed diff, based on git diff -U999;
getting consistent about the term "verbose output" on updated manpage.

I would need an approval from src once again (@des @gbe @kevans );
considering an implicit approval from doc - as the final diff presented here didn't touch any manpage since their last approval.

remove the number of times kernel was compiled from the verbose output of freebsd-version -kv;

this gives this output only 2 columns, instead of 3.

In D27318#821420, @kevans wrote:

Thanks!

Approved by: kevans (src)

thanks for accepting this revision @pauamma
we shall just get an OK from @gbe and/or @kevans and this is good to be committed. right?

In D27318#821022, @pi wrote:

See also PR#265789, it would help if

freebsd-version -rku and -kru did not print the same regardless of the sequence of CLI arguments.

So if some patch for that would be added to this review, that would be very helpful.

same as latest change above, removing "FreeBSD" from the output for verbose kernel's version output:

extend verbose output also into the kernel information, using what @kevans recommended for the running_version() too.

implementing suggestions from @pauamma and @kevans

ping? :3

follow changes from D25705, and reflect update into freebsd-version(1)

pulled latest changes from main, than rebased into it.

ping?

ACK