OvmfPkg: IndustryStandard: factor out Virtio095Net.h

OvmfPkg: IndustryStandard: factor out Virtio095Net.h

In the upcoming virtio-1.0 series, we'll introduce "Virtio10Net.h".
However, the "VirtioNet.h" header file should continue to expose the
Virtio Network Device specific type and macro definitions for all virtio
versions that OvmfPkg supports. Therefore extract "Virtio095Net.h" like
this:

  VirtioNet.h -> Virtio095Net.h

so that in the upcoming patches, we can insert "Virtio10Net.h" in the
middle of the inclusion chain.

This follows the example of "Acpi.h" and "Pci.h" under
"MdePkg/Include/IndustryStandard".

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Suggested-by: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>