extract method: suggested names for folded params should be unique (IDEA-120974)

java/java-tests/testData/refactoring/extractMethod/FoldedParamNameSuggestion.java

@@ -0,0 +1,6 @@
+class Test {
+    String get(String[] args) {
+        <selection>String arg = args[0];
+        return arg;</selection>
+    }
+}

java/java-tests/testData/refactoring/extractMethod/FoldedParamNameSuggestion_after.java

@@ -0,0 +1,10 @@
+class Test {
+    String get(String[] args) {
+        return newMethod(args[0]);
+    }
+
+    private String newMethod(String arg1) {
+        String arg = arg1;
+        return arg;
+    }
+}