Incorrect semantic_type of the physical table.

[WenyXu]

          > We can start by mocking the usage of GreptimeDB as Prometheu's backend(https://docs.greptime.com/user-guide/write-data/prometheus)

We always create two physical table with two columns: a timestamp(millisecond, datatypes) column and a value(double) column. The datatype is following the Prometheus document).

i.e.,

CREATE TABLE phy (ts timestamp time index, val double) engine=metric with ("physical_metric_table" = "");

Then we will get a physical table.

select column_name, data_type, semantic_type  from information_schema.columns where table_name = 'phy';
+-------------+--------------+---------------+
| column_name | data_type    | semantic_type |
+-------------+--------------+---------------+
| ts          | timestamp(3) | TIMESTAMP     |
| val         | double       | FIELD         |
+-------------+--------------+---------------+

Then, the fuzz target randomly creates many logical tables and validates the datatypes of the logical and physical table.

e.g.,

CREATE TABLE t2 (ts timestamp time index, val double, host string, idc string, primary key(idc, host)) engine = metric with ("on_physical_table" = "phy");

Validating the datatypes of the physical table.

select column_name, data_type, semantic_type, column_default from information_schema.columns where table_name = 'phy'; 
+-------------+-----------------+---------------+----------------+
| column_name | data_type       | semantic_type | column_default |
+-------------+-----------------+---------------+----------------+
| ts          | timestamp(3)    | FIELD         | NULL           |
| val         | double          | FIELD         | NULL           |
| __table_id  | int unsigned    | TAG           | NULL           |
| __tsid      | bigint unsigned | TAG           | NULL           |
| host        | string          | TAG           | NULL           |
| idc         | string          | TAG           | NULL           |
+-------------+-----------------+---------------+----------------+

Validating the datatypes of the logical table.

select column_name, data_type, semantic_type, column_default from information_schema.columns where table_name = 't2';
+-------------+--------------+---------------+----------------+
| column_name | data_type    | semantic_type | column_default |
+-------------+--------------+---------------+----------------+
| host        | string       | TAG           | NULL           |
| idc         | string       | TAG           | NULL           |
| ts          | timestamp(3) | TIMESTAMP     | NULL           |
| val         | double       | FIELD         | NULL           |
+-------------+--------------+---------------+----------------+

BTW, there is the bug. The semantic_type in the 1st row should be TIMESTAMP.

select column_name, data_type, semantic_type, column_default from information_schema.columns where table_name = 'phy'; 
+-------------+-----------------+---------------+----------------+
| column_name | data_type       | semantic_type | column_default |
+-------------+-----------------+---------------+----------------+
| ts          | timestamp(3)    | FIELD         | NULL           |
| val         | double          | FIELD         | NULL           |
| __table_id  | int unsigned    | TAG           | NULL           |
| __tsid      | bigint unsigned | TAG           | NULL           |
| host        | string          | TAG           | NULL           |
| idc         | string          | TAG           | NULL           |
+-------------+-----------------+---------------+----------------+

Originally posted by @WenyXu in #3756 (comment)