Feat split tree dropdown question

[Lainow]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !41364
• Here is a brief description of what this PR does
  Added a new question type called Tree Cascade Dropdown, allowing the names of ITIL Locations and Categories to be separated into several dropdowns. (As the splitcat plugin did).

Screenshots (if appropriate):

Before

After

[ccailly]

I tried it and it works pretty well.
However, I think you forgot to handle the advanced configuration of the extended question type.
If I choose an item other than the default root as the root, it seems to break.

By the way, it would probably be more relevant to extend QuestionTypeItemDropdown rather than QuestionTypeItem. Certain specific behaviors are required for CommonTreeDropdown (this case, for example: glpi-project/glpi#19967).
The QuestionTypeItemDropdown class probably cannot be extended at present; a fix would need to be made to the core to remove the final attribute.