Fix for KT-13695, KT-13159 J2K: Invalid conversion context setup for plain text pastes

Extending, Implementing, imports from paste target file previously not implemented

idea/testData/copyPaste/plainTextConversion/Override.expected.kt

@@ -0,0 +1,6 @@
+import test.JavaParent
+
+class KotlinChild : JavaParent() {
+    override fun subject() {
+    }
+}