Support producing static XCFrameworks that is importable from Swift

[thii]

Assuming this would fall into framework_type = ["static"] (not sure why this is a list) in the apple_xcframework rule.

In the meantime, users can use apple_static_xcframework with a post-process to add module map files, but note that XCFrameworks produced this way aren't usable as-is from normal Xcode Swift projects.

[keith]

@kaylathar mentioned offline that someone was looking at this, I believe it's just because the underlying apple_static_library isn't aware of any of these things