### 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)

def test_table_existence_trigger_serialization(self, table_existence_trigger):
        """
        Asserts that the BigQueryTableExistenceTrigger correctly serializes its arguments and classpath.
        """
        classpath, kwargs = table_existence_trigger.serialize()
        assert classpath == "airflow.providers.google.cloud.triggers.bigquery.BigQueryTableExistenceTrigger"
        assert kwargs == {
            "dataset_id": TEST_DATASET_ID,
            "project_id": TEST_GCP_PROJECT_ID,
            "table_id": TEST_TABLE_ID,
            "gcp_conn_id": TEST_GCP_CONN_ID,
            "poll_interval": POLLING_PERIOD_SECONDS,
            "hook_params": TEST_HOOK_PARAMS,
        }
    @pytest.mark.asyncio
    @async_mock.patch(
        "airflow.providers.google.cloud.triggers.bigquery.BigQueryTableExistenceTrigger._table_exists"
    )
    async def test_big_query_table_existence_trigger_success(