Fix Blueprint SearchConstants Value

Fixed Blueprint constant com.coremedia.blueprint.cae.search.SearchConstants.FIELDS#CREATION_DATE to lower-case value creationdate as used in the Solr schema.

(CMS-28592)

Studio Multi-Preview can Change or Disappear Depending on User Permissions

Multi-Preview settings retrieval failed to use the correct read permissions. This can lead to changing or even disappearing Multipreviews in Studio, depending on the permissions.

This behavior was fixed so that a consistent settings retrieval using the correct read permissions is guaranteed.

(CMS-28574)