Make access_check_ddl check for entity privileges.

Function access_check_ddl checked only for universal access, thus
granting entity or singe object access to a user would have no effect in
scope of this function.
Fix this by adding entity access checks.

Also attaching an existing sequence to a space checked for
create privilege on both space and sequence
(instead of read + write on sequence). Fixed it and changed the tests
accordingly.

Closes #3516