Remove $FreeBSD$: one line sh-pattern

Remove the $FreeBSD$ pattern added to the tests, as well as fixing the
mkimg_test.sh script to stop adding it when we rebase the tests.

Reviewed by: imp, emaste
Pull Request: https://github.com/freebsd/freebsd-src/pull/870

Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

base: Remove support for the VTOC8 partitioning scheme

The removal of the sparc64 support in February 2020 obsoleted the
VTOC8 partitioning scheme as no other FreeBSD platform makes use
of it. Moreover, the code is bitrotting as nothing defines e. g.
LOADER_VTOC8_SUPPORT any more and, thus, should go now, too. With
this change, the following commits are reverted as far as VTOC8
is concerned and parts haven't already previously been deleted
along with prior sparc64 removals:
094fcb157d4c98211899cf09d06e2cf19149b7e0
a7d366e9589c95feda6f3bc78c59c6355d51f126
ba8d50d08b9df4e8213f9a6997ff6792ecebcd9b

The alignment example d9711c28efc4ec89ba5ea11f8fd63e9d0a7fc81b
added to the VTOC8 section of gpart.8 is folded into the MBR one.

This should finally conclude the deorbit of sparc64-specific bits.

We had joy, we had fun
we ran Unix on a Sun.
But that source and the song
of FreeBSD have all gone.

Credits to Michael Bueker for the original "Unix on a Sun" and Rod
McKuen for the "Seasons in the Sun" lyrics.

Significantly speed up mkimg_test

It turns out that the majority of the test time for the mkimg tests isn't
mkimg itself but rather the use of jot and hexdump which can be quite slow
on emulated platforms such as QEMU.

On QEMU-RISC-V this reduces the time for `kyua test mkimg_test` from 655
seconds to 200. And for CheriBSD on QEMU-CHERI this saves 4-5 hours (25%
of the time for the entire testsuite!) since jot ends up triggering slow
functions inside the QEMU emulation a lot.

Reviewed By: lwhsu
Differential Revision: https://reviews.freebsd.org/D26796

Add VHDX support to mkimg(1)

VHDX is the successor of Microsoft's VHD file format. It increases
maximum capacity of the virtual drive to 64TB and introduces features
to better handle power/system failures.

VHDX is the required format for 2nd generation Hyper-V VMs.

Reviewed by: marcel
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D25184

Don't compress and uuencode the "hexdump -C" output files. Just
save them with the $FreeBSD$ tag prepended. Changes to these
files are now a lot easier to comprehend, which makes diffs also
reviewable.

Rename tests from <foo> to <foo>_test to match the FreeBSD test suite
naming scheme

usr.bin/diff/diff_test was renamed to usr.bin/diff/netbsd_diff_test
to avoid collisions with the renamed FreeBSD test.

MFC after: 1 week
Sponsored by: Dell EMC Isilon