[TASK] Update unit test expectation for up-and-coming 6.3
[TASK] Switch from static FlashMessage queuing to instances

Recent changes in core require this update.
[TASK] Use namespaces for PHP standard classes
[TASK] Remove unnecessary and unused aliases
[TASK] Add missing aliases
[TASK] Fix typo in alias and annotation
[TASK] Use correct TYPO3 class name in annotation
[TASK] Use correct return type in annotation
[TASK] Remove Exception from annotation
* because there is no Exception thrown
[BUGFIX] Fix property assignment
[BUGFIX] Fix position of extensionKey retrieval

In case of none-empty description string starting with 'LLL:EXT' the $extensionKey is needed.
[TASK] Use ExtensionNamingUtility for extension key extraction
- in order to safely support vendor names