Add documents tab to a few models

[Lainow]

Checklist before requesting a review

Please delete options that are not relevant.

• I have read the CONTRIBUTING document.
• I have performed a self-review of my code.
• I have added tests that prove my fix is effective or that my feature works.
• This change requires a documentation update.

Description

• It fixes !39740
• Here is a brief description of what this PR does

Added the Document tab to the following models:

• DatabaseInstance
• Rack
• ComputerModel
• MonitorModel
• NetworkEquipmentModel
• PeripheralModel
• PhoneModel
• PrinterModel
• DeviceGenericModel
• AssetModel

It is now possible to add documents to all of these models.

Screenshots (if appropriate):

[cedric-anne]

I think custom asset models should also be added automatically to $CFG_GLPI['document_types'].

[cedric-anne]

You added the document tab to asset definitions, but it should rather be added to Glpi\Asset\AssetModel concrete classes.