Kit: move types from WireGuardKit to WireGuardKitTypes.

This prevents linking against wg-go when 3rd-party application needs to
use the WireGuardKit types from within the main bundle, therefore
prevents wg-go from spinning off Golang threads where not applicable.

Signed-off-by: Andrej Mihajlov <and@mullvad.net>

Sources/WireGuardKit/DNSResolver.swift

@@ -4,6 +4,10 @@
 import Network
 import Foundation
 
+#if SWIFT_PACKAGE
+import WireGuardKitTypes
+#endif
+
 enum DNSResolver {}
 
 extension DNSResolver {