Move XWikiPreferences to the xwiki-enterprise-ui-common

XE-1371 moved XWikiPreferences to the admin-user module because the admin user did not have rights, however, this forces anyone that wants to have a package that contains or extends/transforms XWikiPreferences to also depend on admin-user, which is wrong.

Instead, we should move XWikiPreferences to the xwiki-enterprise-ui-common module (or even to its own module?) and have any module that depends on XWikiPreferences (ui-admin-user, ui-wiki, etc.) apply transformations at build time using the xar-plugin instead of forking the file.