Naming considerations for BoundingRect

[kylebarron]

Thanks for the tip on the native impl, I'll move to using that instead.

As far as naming goes (one of the truly hard problems in code), after looking at both the trait and the struct, I'm wondering if renaming the struct to Bounds might end up being a bit more appropriate. It seems like keeping geo::BoundingRect in line with the geo crate is important for discoverability/parity between this crate and geo. Additionally, the native BoundingRect struct includes an optional Z dimension (and I suspect potentially M at some point in the future) which, if we're being pedantic, makes it optionally not a "Rectangle." Other options might be something like Bbox or Extent, but those already feel like overloaded terms in the various "geo" code bases that exist.

Originally posted by @BlakeOrth in #979