Filter locked out users from the participant list

[ostcar]

Currently, all users are shown in the participant list, the the user can see them.

This results in strange behaviours, when a user is locked out from the meeting.

If the blocked user is liked in another object (list of speeker, motion submitter etc) he is shown in the participant list, but not in other cases.

For this reason, we want to change the autoupdate, that blocked users can be seen with user.can_see, but they should get filtered in the client.

This means: If the user does not have user.can_see_sensitive_data, the user participant list should filter users, that are locked out.

See OpenSlides/openslides-autoupdate-service#970