[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/increment.kt

@@ -8,4 +8,4 @@ fun foo(x: Int) {
     println(y)
 }
 
-// LINES: 9 2 2 3 3 4 4 5 5 6 6 7 7 8 8
+// LINES: 1 9 2 2 3 3 4 4 5 5 6 6 7 7 8 8