By default, show times in admin grids in the store timezone.

fixes #9426

This test basically said, use the column config value, or use FALSE:

    $timezone = isset($this->getConfiguration()['timezone'])
        ? $this->booleanUtils->convert($this->getConfiguration()['timezone'])
        : false;

The only config values currently present in the code set the 'timezone'
config to FALSE using `<timezone>false</timezone>`. There are 0 occurances
of `<timezone>true</timezone>` in the code base at this time. This makes
me believe that the default value should not be FALSE but TRUE. Otherwise
the outcome will always be FALSE, be it explicit or by default.

This way the product review created_at times will be the same in the
catalog/product/edit adminhtml page as well as on the Marketing | Reviews
grid. They were not equal before this commit.

The same goes for the CMS page grid, the CMS block grid, the customer grid,
the online customers grid, and the sales grids.

I believe admins wint to see these times in their configured time zone and
not in UTC. Otherwise someone can appear to have placed an order in the
future which is very confusing.

app/code/Magento/Ui/Component/Listing/Columns/Date.php

@@ -57,7 +57,7 @@ public function prepareDataSource(array $dataSource)
                     $date = $this->timezone->date(new \DateTime($item[$this->getData('name')]));
                     $timezone = isset($this->getConfiguration()['timezone'])
                         ? $this->booleanUtils->convert($this->getConfiguration()['timezone'])
-                        : false;
+                        : true;
                     if (!$timezone) {
                         $date = new \DateTime($item[$this->getData('name')]);
                     }