### 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)

"""
    Initialize the BigQuery Table Partition Existence Trigger with needed parameters
    :param partition_id: The name of the partition to check the existence of.
    :param project_id: Google Cloud Project where the job is running
    :param dataset_id: The dataset ID of the requested table.
    :param table_id: The table ID of the requested table.
    :param gcp_conn_id: Reference to google cloud connection id
    :param hook_params: params for hook
    :param poll_interval: polling period in seconds to check for the status
    """
    def __init__(self, partition_id: str, **kwargs):
        super().__init__(**kwargs)
        self.partition_id = partition_id
    def serialize(self) -> tuple[str, dict[str, Any]]:
        """Serializes BigQueryTablePartitionExistenceTrigger arguments and classpath."""
        return (
            "airflow.providers.google.cloud.triggers.bigquery.BigQueryTablePartitionExistenceTrigger",
            {
                "partition_id": self.partition_id,
                "dataset_id": self.dataset_id,
                "project_id": self.project_id,
                "table_id": self.table_id,
                "gcp_conn_id": self.gcp_conn_id,
                "poll_interval": self.poll_interval,
                "hook_params": self.hook_params,
            },
        )
    async def run(self) -> AsyncIterator[TriggerEvent]: