[JS BE] Make sourceMap generation more precise

- Don't produce mapping for closing bracket in case of expressionBody
 - Map Kt*Function declaration into corresponding js fun declaration
 - Update test data & add new test

js/js.translator/testData/lineNumbers/innerClass.kt

@@ -6,4 +6,4 @@ class A(val x: Int) {
     }
 }
 
-// LINES: 1 1 2 2 5 4 4
+// LINES: 1 1 2 2 3 5 4 4