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-object-rest-spread/test/fixtures/object-rest/assignment-expression/expected.js

@@ -1,9 +1,13 @@
 var _c2;
 
-({ a1 } = c1);
+({
+  a1
+} = c1);
 var _c = c2;
-({ a2 } = _c);
+({
+  a2
+} = _c);
 b2 = babelHelpers.objectWithoutProperties(_c, ["a2"]);
-
-
-console.log((_c2 = c3, ({ a3 } = _c2), b3 = babelHelpers.objectWithoutProperties(_c2, ["a3"]), _c2));
+console.log((_c2 = c3, ({
+  a3
+} = _c2), b3 = babelHelpers.objectWithoutProperties(_c2, ["a3"]), _c2));