More readable binarySearch at 4x worst-case cost.

More readable binarySearch at 4x worst-case cost.

With this hopefully more readable version, looking for an unknown
usage and region will result in the binary search being repeated four
times.

The previous version did not use a metadata instance comparator so
that individual components of the metadata key could be compared. A
comparator that returns status information on which of the components
had been found would be able to improve on this.