SQL std auth - make role/user optional in grant/revoke statements

Follow up task of HIVE-5923.
Grant privilege and revoke privilege statements need to be changed to remove the requirement to specify whether the grantee is a user or role. That is, today Hive’s syntax is GRANT action ON [TABLE] table TO grantee where grantee is USER|ROLE identifier.
If the keyword is not specified, hive will try to find role with that matches the identifier, otherwise, it will assume it is a user.