Add `BoundingRegionBuilder::toGlobeRectangle`

[kring]

A small PR that allows the rectangle of a BoundingRegionBuilder to be accessed directly, without needing to construct a BoundingRegion, which is a much more time-consuming thing to do.

[j9liu]

@kring I went ahead and added GlobeRectangle::equals and GlobeRectangle::equalsEpsilon. Since my # changed lines is probably larger than yours now, do you want to look over my changes and merge? 😅

[kring]

Looks great @j9liu, thanks for adding the extra GlobeRectangle tests, too!