Added name field to template_fields in EmrServerlessStartJobOperator

[sseung00921]

closes: #35341

1. Added name field to template_fields in EmrServerlessStartJobOperator as requested in issue Would it be possible to add 'name' to the list of template fields for EmrServerlessStartJobOperator? #35341.
2. Moved default name setting operation from constructor to execute method
3. Updated EmrServerlessStartJobOperator test class

Since self.name = name or self.config.pop("name", f"emr_serverless_job_airflow_{uuid4()}") code is in operator constructor, error occurs in specific situation .
As Taragolis showed well in below comment, if name param is not given and config is given no dict type, error occurs. For example, if config is given by upstream operator (like the example in below comment), error occurs because the type of config is PlainXComArg in this case . And it is a kind of bug which should be fixed.

If the problematic section of code is moved from constructor to execute method, the returned_value of upstream operator is converted to dict type (I do not know the exact principle but checked the fact). So the error above does not occur. So I moved the pop operation to execute method. And I think It might be what @Taragolis intended in his first guide.

I'm a beginner. If I am missing something, comments will make me better :)

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[Taragolis]

My initial point was, that this operator won't work well with all cases of templated fields around of name, so better fix it now and test, rather then keep of "one day in the future"

Example when this operator would fail during initialisation

import pendulum

from airflow.decorators import task
from airflow.models.dag import DAG
from airflow.providers.amazon.aws.operators.emr import EmrServerlessStartJobOperator

SPARK_JOB_DRIVER = {
    "sparkSubmit": {
        "entryPoint": "spam",
        "entryPointArguments": ["s3://spam/egg/output"],
        "sparkSubmitParameters": "--conf spark.executor.cores=1 --conf spark.executor.memory=4g\
            --conf spark.driver.cores=1 --conf spark.driver.memory=4g --conf spark.executor.instances=1",
    }
}

SPARK_CONFIGURATION_OVERRIDES = {
    "monitoringConfiguration": {"s3MonitoringConfiguration": {"logUri": "s3://spam/egg/logs"}}
}

with DAG(
    "pr_35648",
    start_date=pendulum.datetime(2023, 6, 1, tz="UTC"),
    schedule=None,
    catchup=False,
    tags=["pr", "35648"]
):

    @task
    def emr_config():
        return {
            "name": "new_application"
        }

    config = emr_config()

    EmrServerlessStartJobOperator(
        task_id="create_emr_serverless_task",
        application_id="foo",
        aws_conn_id=None,
        release_label="emr-6.6.0",
        job_type="SPARK",
        config=config,
        configuration_overrides={},
        execution_role_arn="foo-bar",
        job_driver=SPARK_JOB_DRIVER
    )

...
    self.name = name or self.config.pop("name", f"emr_serverless_job_airflow_{uuid4()}")
AttributeError: 'PlainXComArg' object has no attribute 'pop'

I have no objection to add only name as templated field and keep it for "better time" in the future. But I think it is a good time to fix this behaviour.

[sseung00921]

@Taragolis I will look into it. Thanks!