[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/jsCode.kt

@@ -5,4 +5,4 @@ fun foo() {
     println("after: $x")
 }
 
-// LINES: 6 2 2 3 3 4 4 5 5
+// LINES: 1 6 2 2 3 3 4 4 5 5