Incorrect return value with tconn.execute_query('insert')

Describe the bug
Execute raw sql insert, result is incorrect.

To Reproduce

from tortoise import Tortoise, fields, run_async
from tortoise.models import Model


class Event(Model):
    id = fields.IntField(pk=True)
    name = fields.TextField()

    class Meta:
        table = "event"

    def __str__(self):
        return self.name


async def run():
    # await Tortoise.init(db_url="sqlite://:memory:", modules={"models": ["__main__"]})
    await Tortoise.init(db_url="postgres://user:pass@127.0.0.1:5432/example", modules={"models": ["__main__"]})
    await Tortoise.generate_schemas()

    from tortoise.transactions import in_transaction
    try:
        async with in_transaction() as tconn:
            r = await tconn.execute_query("insert into event values (10, '2')")
            print(r)
            
            print(await tconn.execute_query('select * from event'))
    except Exception as e:
        print(e)
        await tconn.rollback()

if __name__ == "__main__":
    run_async(run())


# You got this:
# (0, [])
# (6, [<Record id=1 name='2'>])

# Sqlite got this:
(1, [])
(1, [<sqlite3.Row object at 0x00000208DDA86ED0>])

Expected behavior
(1, [])

Additional context
It would be better to return lastrowid

The entry point is the transaction connection's execute_query, with the reproduction comparing PostgreSQL and SQLite INSERT results; start there and compare both backend paths. Add a regression test for an INSERT and verify that the returned result matches the expected row-count and last-row information for each backend.