### Apache Airflow version

main (development)

### What happened

1. When not providing `project_id` to `BigQueryGetDataOperator` in deferrable mode (`project_id=None`), the query generated by `generate_query` method is bugged, i.e.,: 

````sql
from `None.DATASET.TABLE_ID` limit ...
````

2. `as_dict` param does not work `BigQueryGetDataOperator`.

### What you think should happen instead

1. When `project_id` is `None` - it should be removed from the query along with the trailing dot, i.e.,:

````sql
from `DATASET.TABLE_ID` limit ...
````

2. `as_dict` should be added to the serialization method of `BigQueryGetDataTrigger`.

### How to reproduce

1. Create a DAG file with `BigQueryGetDataOperator` defined as follows:
```python
BigQueryGetDataOperator(
        task_id="bq_get_data_op",
        # project_id="PROJECT_ID",  <-- Not provided
        dataset_id="DATASET",
        table_id="TABLE",
        use_legacy_sql=False,
        deferrable=True
    )
````

2. 1. Create a DAG file with `BigQueryGetDataOperator` defined as follows:
```python
BigQueryGetDataOperator(
        task_id="bq_get_data_op",
        project_id="PROJECT_ID",
        dataset_id="DATASET",
        table_id="TABLE",
        use_legacy_sql=False,
        deferrable=True,
        as_dict=True
    )
````

### Operating System

Debian

### Versions of Apache Airflow Providers

_No response_

### Deployment

Official Apache Airflow Helm Chart

### Deployment details

_No response_

### Anything else

The `generate_query` method is not unit tested (which would have prevented it in the first place) - will be better to add one.

### Are you willing to submit PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

gcp_conn_id="google_cloud_default",
            udf_config=None,
            use_legacy_sql=True,
            maximum_billing_tier=None,
            maximum_bytes_billed=None,
            create_disposition="CREATE_IF_NEEDED",
            schema_update_options=(),
            query_params=None,
            labels=None,
            priority="INTERACTIVE",
            time_partitioning=None,
            api_resource_configs=None,
            cluster_fields=None,
            encryption_configuration=None,
        )
        operator.execute(MagicMock())
        mock_hook.return_value.run_query.assert_has_calls(
            [
                mock.call(
                    sql="Select * from test_table",
                    destination_dataset_table=None,
                    write_disposition="WRITE_EMPTY",
                    allow_large_results=False,
                    flatten_results=None,
                    udf_config=None,
                    maximum_billing_tier=None,
                    maximum_bytes_billed=None,
                    create_disposition="CREATE_IF_NEEDED",
                    schema_update_options=(),
                    query_params=None,