Add allow_to_edit_own_delegation

[Elblinator]

See OpenSlides/OpenSlides#6223 for context

Desired behaviour:

We have a new setting which allows to delegate your own vote (allow_to_edit_own_delegation)

And a group permission, which allows user from this group to delegate their own vote (user.can_edit_own_delegation)

A participant should be allowed to delegate their own delegation to whoever they want AND they should be allowed to remove the delegation from another person to themselves

Can edit own delegation needs the permission ‚Can see participants‘