Add possibility for manually switching participants from / to waitinglist

Tasks for first implementation version (which might already be good enough):

Participant Form:

[x] Add "..." and place two entries in there (already existing musterdata-filling and move participant in list)
[x] Dialog shows up for Move Participant in List: Allow selection of participant (from list in select-box) which should be swapped)
[x] Don't show child partiicipants of team partner wish registrations in this list (or maybe include them in displayname of root-participant in list)
[x] Show warning when teams already exist (for selected participants) => Team arrangements must firstly be cancelled again
[x] Reload participant list after change

Team list:

[x] Enhance "Regenerate teams" link to be a dropdown with two items (alredy existing "Regenerate teams" and new entry "Clear Team Arrangements")
[x] Dialog shows up with info about clearing team arrangements (quite similar to regeneration)
[x] Enhance now also regenerate dialog with info about that existing team partner wishes will again be fullfilled.
[x] Add possibility for directly open drop teams dialog in teams view (by link query param)

Backend:

[x] New endpoint for teams for just clearing team generations
[x] New endpoint for participants which gets two participant Ids and switch their participant-number (check before, that teams are not existing)
[x] Add check in backend for not using same participant-id
[x] Consider child / root team partner wishes (when child is moved up, then re-sort all entries so that child is exactly below root)
[x] Root partner may always also move child partner
[x] Add own activity for drop teams
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Clemens85 / runningdinner