openssh: update to OpenSSH v8.7p1

Some notable changes, from upstream's release notes:

- sshd(8): Remove support for obsolete "host/port" syntax.
- ssh(1): When prompting whether to record a new host key, accept the key
fingerprint as a synonym for "yes".
- ssh-keygen(1): when acting as a CA and signing certificates with an RSA
key, default to using the rsa-sha2-512 signature algorithm.
- ssh(1), sshd(8), ssh-keygen(1): this release removes the "ssh-rsa"
(RSA/SHA1) algorithm from those accepted for certificate signatures.
- ssh-sk-helper(8): this is a new binary. It is used by the FIDO/U2F
support to provide address-space isolation for token middleware
libraries (including the internal one).
- ssh(1): this release enables UpdateHostkeys by default subject to some
conservative preconditions.
- scp(1): this release changes the behaviour of remote to remote copies
(e.g. "scp host-a:/path host-b:") to transfer through the local host
by default.
- scp(1): experimental support for transfers using the SFTP protocol as
a replacement for the venerable SCP/RCP protocol that it has
traditionally used.

Additional integration work is needed to support FIDO/U2F in the base
system.

Deprecation Notice
------------------

OpenSSH will disable the ssh-rsa signature scheme by default in the
next release.

Reviewed by: imp
MFC after: 1 month
Relnotes: Yes
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D29985

Upgrade to OpenSSH 7.9p1.

MFC after: 2 months
Sponsored by: The FreeBSD Foundation

Upgrade to OpenSSH 7.7p1.

Upgrade to OpenSSH 6.9p1.

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 4.3p1.

Vendor import of OpenSSH 3.9p1.

Vendor import of OpenSSH 3.8.1p1.

Vendor import of OpenSSH 3.8p1.

Vendor import of OpenSSH 3.7.1p2.

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 4.3p1.

Vendor import of OpenSSH 3.9p1.

Vendor import of OpenSSH 3.8.1p1.

Vendor import of OpenSSH 3.8p1.

Vendor import of OpenSSH 3.7.1p2.