It turned out that the latest version of APEX (3.1.2, or maybe some oldest versions as well, don't have these to check out) does use result_cache hint for a queries like this:
SELECT /*+ result_cache */ MESSAGE_TEXTBoth of these queries are simple lookups...
WHERE SECURITY_GROUP_ID = 10
AND MESSAGE_LANGUAGE = :B2
AND NAME = UPPER(:B1 )
SELECT /*+ result_cache */ NLS_LANGUAGE, NLS_TERRITORY, NLS_SORT, NLS_WINDOWS_CHARSET
WHERE LANG_ID_UPPER = UPPER(:B1 )