Possible cache inconsistency when asked XWikiDocument has a different wiki than the one in the context

Hibernate store loadXWikiDoc(XWikiDocument doc, XWikiContext context) implementation does not take into account doc wiki and search in the current database. This always been like this and a known behavior.

The problem is that XWikiCacheStore#loadXWikiDoc does not take into account the context when calculating the document cache key and might end up associating the document currentwiki:Space.Page with the key docwiki:Space.Page.

We don't have much issue with that because XWiki#getDocument is taking care of updating the context based on the document wiki but it's still dangerous.

There is several possibility:

1. stop searching in the context wiki and search in the document wiki instead
2. calculate the new key based on the found instance

1 is probably what makes more sense but since it's a behavior change it's probably a discussion for another time and another API probably, one not passing a context to be explicit.