block: vhdx - add region overlap detection for image files

Regions in the image file cannot overlap - the log, region tables,
and metdata must all be unique and non-overlapping.

This adds region checking by means of a QLIST; there can be a variable
number of regions and metadata (there may be metadata or region tables
that we do not recognize / know about, but are not required).

This adds the capability to register a region for later checking, and
to check against registered regions for any overlap.

Also, if neither the BAT or Metadata region tables are found, return
error.

Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>