Remove whitespace generation (#5833)

* Remove whitespace generation and rely on default printing

Changes to printing:
* Add newline after last empty SwitchCase
* Add newlines around block comments if they are non-flow comments or contain newlines

* Fix a few more fixtures

packages/babel-plugin-transform-es2015-function-name/test/fixtures/function-name/assignment/expected.js

@@ -3,7 +3,11 @@ var _i = function i() {
 };
 
 var _j = function j() {
-  ({ j: _j } = 5);
-  ({ y: _j } = 5);
+  ({
+    j: _j
+  } = 5);
+  ({
+    y: _j
+  } = 5);
   ;
-};
+};