feat(query): add identifier function from session variable

[sundy-li]

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Summary

support identifier($name)

> CREATE TABLE monthly_sales(empid INT, amount INT, month TEXT) as select 1,2,'3';
Query OK, 1 row affected (0.11 sec)

> set variable t = 'monthly_sales';
Query OK, 0 rows affected (0.01 sec)

 
> select * from  identifier($t);
+-------+--------+-------+
| empid | amount | month |
+-------+--------+-------+
|     1 |      2 | 3     |
+-------+--------+-------+
1 row in set (0.05 sec)
Read 1 rows, 28.00 B in 0.019 sec., 52.34 rows/sec., 1.43 KiB/sec.

Part of #16135

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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This change is