Remove swift_usage_aspect and SwiftUsageInfo

[luispadron]

Cherry-picked from commit: c24a84a

With the toolchain information removed, this aspect/provider offers a minimal API. The only client is rules_apple, which uses it to determine if Swift support may need to be bundled at all, so it's better that that single client own it, rather than rules_swift try to provide an API that could serve all possible hypothetical clients.