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 #5682: The `asset` command would incorrectly combine CSS files when `UrlManager::linkAssets` is true

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

Fixes #5665: The `currentPage` meta data in the RESTful result should be 1-based, similar to that in HTTP headers

#4471: `yii\caching\ApcCache` now returns array in case of APC is installed but not enabled in CLI mode

Fixes #4457: Added support for using noscript for css files registered through asset bundles and Html helper

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 #5598: added ImageMagick with PNG and GD with FreeType checks to requirements of basic and advanced applications, used better Captcha exception message

fixes #5601

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

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

Fixes #5584: `yii\rbac\DbRbacManager` should not delete items when deleting a rule on a database not supporting cascade update

before: failed with undefined index PHP error
now: fail with proper error complaining about missing argument.

ensure syntax highlighting

there is no reliable way to determine the cubrid PDO extension version used
and also no reliable way to detect which combination of server and client produces wrong behavior.

By requiering 9.3 or higher in both client and server we can be sure it works.

fixes #852