WIP: [8381] add new poll module

[goapunk]

To test create a new module (Open Poll) and allow unregistered users in the module settings.

Depends on https://github.com/liqd/adhocracy4/pull/1681

Tasks

• [x] PR name contains story or task reference
• [ ] Documentation (docs and inline)
• [ ] Tests (including n+1 and django_assert_num_queries where applicable)
• [ ] Changelog

[goapunk]

@m4ra @hom3mad3 this is ready for a first round of reviewing (most changes are in a4), there's probably not a lot of frontend as we want to refactor that anyway, I just made it work for now. Also still need to add more docs

[goapunk]

closing as superseded by #1683 / unnecessary