Fixes for feature "Regroupment of center"

* allow more than 15 character in regroupment name
* remove unused methods in PickCenterType
* show only active Regroupment in form
* remove dead code and commented code

src/Bundle/ChillMainBundle/Entity/Regroupment.php

@@ -43,7 +43,7 @@ class Regroupment
     private bool $isActive = true;
 
     /**
-     * @ORM\Column(type="string", length=15, options={"default": ""}, nullable=false)
+     * @ORM\Column(type="text", options={"default": ""}, nullable=false)
      */
     private string $name = '';