Handle INSERT ... SELECT for one row

[levkk]

#726

Handles this case specifically:

INSERT INTO table_x (id, value) VALUES 1, 'test';

The columns have to be enumerated.

[codecov]

Codecov Report

❌ Patch coverage is 94.97487% with 10 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog/src/frontend/router/parser/statement.rs	94.73%	10 Missing ⚠️

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