[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/conditionalDecomposed.kt

@@ -14,4 +14,4 @@ private inline fun foo(): Int {
     return 23
 }
 
-// LINES: 10 3 3 3 4 3 6 13 13 3 14 2 15 13 13 14 14
+// LINES: 1 10 3 3 3 4 3 6 13 13 3 14 2 12 15 13 13 14 14