Rename the failable map overload to compactMap

[younata]

Yes, I just submitted the PR adding this new matcher. Then I thought on it some more and decided I didn't like the slightly different behavior between 2 different versions of map.

Instead, I renamed the map with optional transform to compactMap (which you can tell from the documentation that this was the original name before I made a decision to rename it to just map), and added another overload of map that takes a closure returning an optional that behaves exactly like how the map without optional behaves.

I also redid the tests to be sure to check all of this.

Checklist - While not every PR needs it, new features should consider this list:

• Does this have tests?
• Does this have documentation?
• Does this break the public API (Requires major version bump)?
• Is this a new feature (Requires minor version bump)?