306 implement multi relation picker for person and try to factorize relation picker (#319)

* Removed useless folder

* First working version

* Refactored MultipleEntitySelect and splitted into 2 components

* Added TODO

* Removed useless Query

* Fixed refetch

* Fixed naming

* Fix tests

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Co-authored-by: Charles Bochet <charles@twenty.com>

front/src/modules/ui/components/menu/DropdownMenu.tsx

@@ -17,6 +17,4 @@ export const DropdownMenu = styled.div`
   height: fit-content;
 
   width: 200px;
-
-  z-index: ${(props) => props.theme.lastLayerZIndex};
 `;