This: 1. Deletes XModuleDescriptorToXBlockMixin 2. Deletes `metadata_traslations` and `_translate()` from `XmlParserMixin`, and all related implementations. 3. Removes translations of deprecated OLX attributes during import/export: <old_attr> : <new_attr> - 'slug' : 'url_name' - 'name' : 'display_name' - 'id' : 'discussion_id' (Discussion XBlock) - 'for' : 'discussion_target' (Discussion XBlock) - 'attempts' : 'max_attempts' (CAPA)
Also fixed things in the toy course where needed
Factories were used when possible but tests depending on importing or things not manageable by factories used the toy course. New files were added to include the needed functionality. Most files are blank or have minimal xml needed to work
