CREATE FOREIGN TABLE LIKE.

[avamingli]

Allow user to use LIKE to create foreign tables, ex:

CREATE FOREIGN TABLE ft(LIKE t1);

Foreign table ft will use t1's column definitions as its own.

In CBDB, we usually use foreign tables to import data from outside data source.
Each target table usually has an associated foreign table.
This is very useful if target table has a lot of columns, making it easy to create a foreign table without defining columns one by one, and avoid mistake.

Distribution policy is not inherited for this case because it should be defined with options by users.

CREATE FOREIGN DATA WRAPPER dummy;
CREATE SERVER s0 FOREIGN DATA WRAPPER dummy;
CREATE TABLE ft_source_table(a INT, b INT, c INT) DISTRIBUTED BY (b);
CREATE FOREIGN TABLE ft_like (LIKE ft_source_table) SERVER s0; 
\d+ ft_like
                                     Foreign table "public.ft_like"
 Column |  Type   | Collation | Nullable | Default | FDW options | Storage | Stats target | Description 
--------+---------+-----------+----------+---------+-------------+---------+--------------+-------------
 a      | integer |           |          |         |             | plain   |              | 
 b      | integer |           |          |         |             | plain   |              | 
 c      | integer |           |          |         |             | plain   |              | 
Server: s0

Authored-by: Zhang Mingli avamingli@gmail.com

fix #ISSUE_Number

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