fix dual

[daviszhen]

What type of PR is this?

• API-change
• BUG
• Improvement
• Documentation
• Feature
• Test and CI
• Code Refactoring

Which issue(s) this PR fixes:

issue #https://github.com/matrixorigin/MO-Cloud/issues/3447

What this PR does / why we need it:

对dual的修改：

CASE 1:
create table dual(a int);
select * from dual;
mysql responses: No tables used
mo和mysql认为是占位符。

CASE 2: select * from dual;
create table dual(a int);
select * from dual;
mysql responses: success.
mysql认为是正常表。
mo认为是占位符。这与mysql不同。目前的parser不好改为同mysql一致。

CASE 3:
create table dual(a int);
select * from db.dual;
select * from icp.dual;
mysql responses: success.
mysql和mo都认为是正常表。