[MOV] doc: move documentation to a dedicated repository

In odoo/documentation#945, the developer documentation is merged
with the user documentation in a single repository and build config.

This commit then removes source files for the developer documentation
from the odoo/odoo repository.

DOC PR: odoo/documentation#945

task-2352371

Co-authored-by: Victor Feyens <vfe@odoo.com>
Co-authored-by: Antoine Vandevenne <anv@odoo.com>

Author: 2 people