include/hw/vfio/vfio-container.h: rename file to vfio-container-legacy.h

include/hw/vfio/vfio-container.h: rename file to vfio-container-legacy.h

With the rename of VFIOContainer to VFIOLegacyContainer, the vfio-container.h
header file containing the struct definition is misleading. Rename it from
vfio-container.h to vfio-container-legacy.h accordingly, fixing up the name
of the include guard at the same time.

Signed-off-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250925113159.1760317-4-mark.caveayland@nutanix.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>