Introduce Parameter: Support extraction of string template fragments

idea/testData/refactoring/introduceParameter/stringTemplates/extractFalse.kt

@@ -0,0 +1,6 @@
+fun foo(param: Int): String {
+    val x = "xyfalsez"
+    val y = "xyFalsez"
+    val z = false
+    return "ab<selection>false</selection>def"
+}