Make module imports public to survive internal imports by default

Maybe resolves #705

Alternatives would be to keep internal imports but that's an adventure
since we need to keep those thunks NOT dead code eliminated... and we
cannot use @used until swift 6.3 so this could not be used in previous
swift builds...

Author: ktoso

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -836,13 +836,15 @@ extension JNISwift2JavaGenerator {
   }
 
   private func printHeader(_ printer: inout CodePrinter) {
+    // `public import` so the thunk file remains valid under
+    // `InternalImportsByDefault` (SE-0409)
     printer.print(
       """
       // Generated by swift-java
 
-      import SwiftJava
-      import SwiftJavaJNICore
-      import SwiftJavaRuntimeSupport
+      public import SwiftJava
+      public import SwiftJavaJNICore
+      public import SwiftJavaRuntimeSupport
 
       """
     )