orderby/select/expand should be oneOf when UseStringArrayForQueryOptionsSchema is false

[baywet]

Currently we describe

parameters:
 - name: $select
 in: query
 style: form
 explode: false
 schema:
 uniqueItems: true
 type: array
 items:
 type: string
 enum:
 - id
 - firstName
 - ....

It should instead be

parameters:
 - name: $select
 in: query
 style: form
 explode: false
 schema:
 uniqueItems: true
 type: array
 items:
 oneOf:
 - type: string
 - type: string
 enum:
 - id
 - firstName
 - ....

This is because for any navigation property you can write $select=navProperty($expand=subproperty) and we don't want to project all possibilities. But we don't want to restrict clients to simply the scalar/first level properties.