[TASK] Deprecated Small/Medium/Standard-Document

Deprecates classes:

- SmallDocumentTemplate
- MediumDocumentTemplate
- StandardDocumentTemplate

These classes are rarely used.
Also the standard style in the backend move along.

Fixes: #45955
Releases: 6.1
Change-Id: Ic6e261eef960a71f56a8c5af4724f24e5da8e32c