[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/closure.kt

@@ -5,4 +5,4 @@ fun box(x: Int, y: Int): Int {
     return foo(y)
 }
 
-// LINES: 2 2 2 4 4 6 2 2 5 5
+// LINES: 2 2 2 4 4 1 6 2 2 5 5