Support swift test for Swift packages

[smolck]

Apologies if I just missed it, but currently there doesn't seem to be a command/picker for testing a Swift package? Just building/running (which for a library, just equates to building).

[kkharji]

Yes, no support for running test for both xcodeproj and swift.

For swift, it should be straightforward, when extracting targets from Package.swift through swift package dump-package you can see which targets are tests targets, in current implementation of SwiftProject I'm ignoring tests from targets. For this to work, the type of targets, rn HashMap<String, PBXTargetPlatform>, needs to allow for target kind, so maybe new type Target.

For the xcodeproj, we might endup deciding which is test and which is not through checking if it prefixed with Test.

From here, we have a new proto Test and a picker.

I suggest making this issue Support Test and swift test as todo item,