MFC 321762
hyperv: Add VF bringup scripts and devd rules.

How network VF works with hn(4) on Hyper-V in non-transparent mode:

- Each network VF has a cooresponding hn(4).
- The network VF and the it's cooresponding hn(4) have the same hardware
address.
- Once the network VF is up, e.g. ifconfig VF up:
o All of the transmission should go through the network VF.
o Most of the reception goes through the network VF.
o Small amount of reception may go through the cooresponding hn(4).
This reception will happen, even if the the cooresponding hn(4) is
down. The cooresponding hn(4) will change the reception interface
to the network VF, so that network layer and application layer will
be tricked into thinking that these packets were received by the
network VF.
o The cooresponding hn(4) pretends the physical link is down.
- Once the network VF is down or detached:
o All of the transmission should go through the cooresponding hn(4).
o All of the reception goes through the cooresponding hn(4).
o The cooresponding hn(4) fallbacks to the original physical link
detection logic.

All these features are mainly used to help live migration, during which
the network VF will be detached, while the network communication to the
VM must not be cut off. In order to reach this level of live migration
transparency, we use failover mode lagg(4) with the network VF and the
cooresponding hn(4) attached to it.

To ease user configuration for both network VF and non-network VF, the
lagg(4) will be created by the following rules, and the configuration
of the cooresponding hn(4) will be applied to the lagg(4) automatically.

Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D11635

MFC r314653:

libexec: normalize paths using SRCTOP-relative paths or :H when possible

This simplifies make logic/output

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

META MODE: Update dependencies with 'the-lot' and add missing directories.

This is not properly respecting WITHOUT or ARCH dependencies in target/.
Doing so requires a massive effort to rework targets/ to do so. A
better approach will be to either include the SUBDIR Makefiles directly
and map to DIRDEPS or just dynamically lookup the SUBDIR. These lose
the benefit of having a userland/lib, userland/libexec, etc, though and
results in a massive package. The current implementation of targets/ is
very unmaintainable.

Currently rescue/rescue and sys/modules are still not connected.

Sponsored by: EMC / Isilon Storage Division

Use LIBEXECDIR for /usr/libexec.

MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division

META MODE: These need object directories to handle staging.

Sponsored by: EMC / Isilon Storage Division

Import HyperV Key-Value Pair (KVP) driver and daemon code by Microsoft,
many thanks for their continued support of FreeBSD.

While I'm there, also implement a new build knob, WITHOUT_HYPERV to
disable building and installing of the HyperV utilities when necessary.

The HyperV utilities are only built for i386 and amd64 targets.

This is a stable/10 candidate for inclusion with 10.1-RELEASE.

Submitted by: Wei Hu <weh microsoft com>
MFC after: 1 week