Adjust searchlimit to new identity auth filter

Context:

In OPT-3247, we started filtering identity search results by the current user's authorizations. As a result, in search queries with a maxResult limit, this could lead to returning a smaller than maxResult or empty search result event though there might be more identities that the user has access to. 

AT:

• when searching with a maxResults limit, only stop once the maxResult limit is hit or once we hit the end of search results
• also, searchIdentities(final String terms) is only used in IT, so can be removed from the cache