### 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)

table_id=self.table_id,
                schema_fields=schema_fields,
                time_partitioning=self.time_partitioning,
                cluster_fields=self.cluster_fields,
                labels=self.labels,
                view=self.view,
                materialized_view=self.materialized_view,
                encryption_configuration=self.encryption_configuration,
                table_resource=self.table_resource,
                exists_ok=self.if_exists == IfExistAction.IGNORE,
            )
            BigQueryTableLink.persist(
                context=context,
                task_instance=self,
                dataset_id=table.to_api_repr()["tableReference"]["datasetId"],
                project_id=table.to_api_repr()["tableReference"]["projectId"],
                table_id=table.to_api_repr()["tableReference"]["tableId"],
            )
            self.log.info(
                "Table %s.%s.%s created successfully", table.project, table.dataset_id, table.table_id
            )
        except Conflict:
            error_msg = f"Table {self.dataset_id}.{self.table_id} already exists."
            if self.if_exists == IfExistAction.LOG:
                self.log.info(error_msg)
            elif self.if_exists == IfExistAction.FAIL:
                raise AirflowException(error_msg)
            else:
                raise AirflowSkipException(error_msg)
class BigQueryCreateExternalTableOperator(GoogleCloudBaseOperator):