INSERT … SELECT does not error out in append/range distributed tables if SELECTed table is same with INSERTed one

We should error out saying “INSERT ... SELECT into an append-distributed table is not supported” as we do for append distributed tables

This happens because according to our definition of colocation, all tables are colocated with itself (even append distributed ones). Thus, below code passes related error checks.

Example test case to reproduce the issue;
```sql
CREATE TABLE append_copy(id integer, data text, int_data int);
SELECT create_distributed_table('append_copy', 'id', 'append');
COPY append_copy FROM PROGRAM 'echo 0, a, 0\\n1, b, 1\\n2, c, 2\\n3, d, 3\\n4, e, 4' WITH CSV;

INSERT INTO append_copy SELECT * FROM append_copy;
INSERT 0 0
```