Fixes #5735: Added `yii\bootstrap\Tabs::renderTabContent` to support manually rendering tab contents

Fixes #5708

Revert "Fixes #3760: Gii model generator now imports classes when necessary instead of using fully qualified class names"

This reverts commit 0c8faedd.

Fixes #3760: Gii model generator now imports classes when necessary instead of using fully qualified class names

Fixes #5570: `yii\bootstrap\Tabs` would throw an exception if `content` is not set for one of its `items`
Fixes #5572.

Fixes #5587: `json_encode` is now used with `JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE` where it makes sense, also it is now default for `Json::encode()`

Fixes #5402: Debugger was not loading when there were closures, resources or PDO instances in the logged data

fixes #5623

fixes #5601

Fixed the bug that Gii console command help information does not contain global options

fixes #5580

Fixes #5600: Allow configuring debug panels in `yii\debug\Module::panels` as panel class name strings

Fixes #5528: added auto_reload to default twig config in both extension readme and template engines chapter in docs