Fix page provider schemas selection in Designer in ui/drawer/left-menu/<ppName>

Summary: the selection of schemas in Designer in the drawer item selection page is broken: it can propose a wrong schema for the confgured page provider,a d when correcting, adds schema in its own

How to reproduce:
In Modeler

• Create 2 schemas Doc1 and Doc2 (each made of a string for instance)
• Create 2 document types doc1 and doc2 and add the previous respective schema (1 schema per document)
• Create 2 page providers pp1 and pp2 specialized in their respective doctypes, e.g. for pp1

  ecm:mixinType != 'HiddenInNavigation' AND ecm:isVersion = 0 AND ecm:isTrashed = 0 and ecm:primaryType='doc1'

  and predicate

  Doc1:string1 STARTSWITH (Doc1_string1)

In Designer

• configure the layouts for doc1 and doc2
• configure the layouts for pp1 and pp2
• add a drawer item for each page provider
• configure each drawer item for their respective schema
  Expected: pp1 should come with Doc1 and pp2 should come with Doc2. This is not the case: pp2 comes with Doc1 if pp1 has been configured first
• correct the schema for pp2: remove Doc1 and add Doc2
  Expected: Doc2 remains, Doc1 drops
  Actuel result: Doc2 is added but Doc1 remains with no way to remove it from this screen

See also attached screenshots.