ssh: update to OpenSSH v8.9p1

Release notes are available at https://www.openssh.com/txt/release-8.9

Some highlights:

* ssh(1), sshd(8), ssh-add(1), ssh-agent(1): add a system for
restricting forwarding and use of keys added to ssh-agent(1)

* ssh(1), sshd(8): add the sntrup761x25519-sha512@openssh.com hybrid
ECDH/x25519 + Streamlined NTRU Prime post-quantum KEX to the
default KEXAlgorithms list (after the ECDH methods but before the
prime-group DH ones). The next release of OpenSSH is likely to
make this key exchange the default method.

* sshd(8), portable OpenSSH only: this release removes in-built
support for MD5-hashed passwords. If you require these on your
system then we recommend linking against libxcrypt or similar.

Future deprecation notice
=========================

A near-future release of OpenSSH will switch scp(1) from using the
legacy scp/rcp protocol to using SFTP by default.

Legacy scp/rcp performs wildcard expansion of remote filenames (e.g.
"scp host:* .") through the remote shell. This has the side effect of
requiring double quoting of shell meta-characters in file names
included on scp(1) command-lines, otherwise they could be interpreted
as shell commands on the remote side.

MFC after: 1 month
Relnotes: Yes
Sponsored by: The FreeBSD Foundation

Upgrade to OpenSSH 7.6p1. This will be followed shortly by 7.7p1.

This completely removes client-side support for the SSH 1 protocol,
which was already disabled in 12 but is still enabled in 11. For that
reason, we will not be able to merge 7.6p1 or newer back to 11.

Upgrade to OpenSSH 7.4p1.

Upgrade to OpenSSH 6.7p1, retaining libwrap support (which has been removed
upstream) and a number of security fixes which we had already backported.

MFC after: 1 week

Upgrade to OpenSSH 6.6p1.

Pull in all the OpenSSH bits that we'd previously left out because we
didn't use them. This will make future merges from the vendor tree much
easier.

Approved by: re (gjb)

Remove a bunch of files we don't need to build OpenSSH. They are still
available in base/vendor-crypto/openssh/dist/.

Properly flatten openssh/dist.

Vendor import of OpenSSH 4.0p1.

Vendor import of OpenSSH 3.9p1.

Vendor import of OpenSSH 3.8.1p1.

Remove a bunch of files we don't need to build OpenSSH. They are still
available in base/vendor-crypto/openssh/dist/.

Vendor import of OpenSSH 4.0p1.

Vendor import of OpenSSH 3.9p1.

Vendor import of OpenSSH 3.8.1p1.