[IMP] base: Make 'name' attribute required for 'filter' tag

Purpose
=======

The attribute name isn't required on the <filter> tag. If not set, it can't be selected with a xpath and it can't be overwritten.

A lot of PR are coming from the community just to add a name on a filter because:
- It can't be selected with a xpath.
- It can't be used with `default_search_foo` on an action context.

Specification
=============

Make the atttribute name required