[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/stringLiteral.kt

@@ -4,4 +4,4 @@ fun box(x: Int): String {
            "suffix"
 }
 
-// LINES: 5 2 2 3 4
+// LINES: 1 5 2 2 3 4