Before this rev. one could set the report layout on the company using a
hardcoded list (background, clean, standard, etc.). Other modules (typically
accounting modules) could add options in this list. The used template was built
on the layout key.

Now, the layout is a many2one field to a newly created model `report.layout`,
which is linked to a view with the layout architecture.

This gives more control to customize reports and create a new layout (without
creating a python module that extend the layout selection).

Specific report template used in Germany. Add a new report layout as well as
a new paperformat.

Was part of task: 35289
Was part of PR #25472

* CoA up to date
* Taxes up to date
* SKR03 installed by default but users can easily switch to SKR04 while no accounting entries exists for the company
* removed unneeded things
* set tags accordingly on accounts and taxes for the reports to work (new reports in enterprise)

Was task 31826. Was PR #17447. Discussion related on #18571