Introduce Variable: Skip leading/trailing comments inside selection

#KT-13054 Fixed

idea/testData/refactoring/introduceVariable/stringTemplates/extractTrueWithSpaces.kt

@@ -0,0 +1,7 @@
+fun foo(param: Int): String {
+    val x = "atrue123"
+    val y = "aTRUE123"
+    val z = true
+    val u = "123 true 456"
+    return "ab<selection> true </selection>def"
+}