SHOW HINT STATUS 语法用于针对当前连接，查询 hint 设置
ShowHintStatus ::=
'SHOW' ('SHARDING' | 'READWRITE_SPLITTING') 'HINT' 'STATUS'
SHARDING 的 hint 设置SHOW SHARDING HINT STATUS;
READWRITE_SPLITTING 的 hint 设置SHOW READWRITE_SPLITTING HINT STATUS;
SHOW、SHARDING、READWRITE_SPLITTING、HINT、STATUS