[Story] Preview for effects of policy list subscription

[Gnuxie]

Description

As a Draupnir moderator, when I find a new policy list to watch, I should be able to preview the effects of watching the list before making a decision to watch it. Effects include any users that will be removed from protected rooms, any servers that would be banned and their effected users in protected rooms. We will also need to be notified of the effects this will have on other protections that might use policy rooms. Then we can click the confirm or cancel the application of the changes.

Acceptance criteria

• When previewing changes to policy subscription, I can see a summary of all the actions that protections would make
• I can decide to accept or cancel the changes

Issues

• Make policy list collaboration easier by offering to preview effects before subscribing Draupnir#192
• Make banlist collaboration easier by offering to preview effects before subscribing matrix-org/mjolnir#228
• (maybe) Preview the effects of enabling a protection Draupnir#359

Dependencies

• [Story] Add capability management to Draupnir and MPS #6 - partially, since the dummy (config.noop replacement) capabilities will need to exist and have their renderers available

Total Pain

40