Add xcom map_index as a filter to xcom endpoint

[hussein-awala]

closes: #32367

This PR add map_index as filter for Xcom endpoints and to their responses, and adds xcom_key as filter for get_xcom_entries.

Here are some examples:

# get all xcom entries for a task instance
curl -X 'GET' \
  'http://localhost:28080/api/v1/dags/test_dynamic_task_mapping/dagRuns/some_run_id/taskInstances/mapped_task/xcomEntries?limit=100' \
  -H 'accept: application/json'
{
  "total_entries": 6,
  "xcom_entries": [
    {
      "dag_id": "test_dynamic_task_mapping",
      "execution_date": "2023-07-09T10:00:00.00+00:00",
      "key": "return_value",
      "map_index": 0,
      "task_id": "mapped_task",
      "timestamp": "2023-07-09T10:19:02.578137+00:00"
    },
    {
      "dag_id": "test_dynamic_task_mapping",
      "execution_date": "2023-07-09T10:00:00.00+00:00",
      "key": "return_value",
      "map_index": 1,
      "task_id": "mapped_task",
      "timestamp": "2023-07-09T10:19:12.624135+00:00"
    },
    {
      "dag_id": "test_dynamic_task_mapping",
      "execution_date": "2023-07-09T10:00:00.00+00:00",
      "key": "return_value",
      "map_index": 2,
      "task_id": "mapped_task",
      "timestamp": "2023-07-09T10:19:22.626682+00:00"
    },
    {
      "dag_id": "test_dynamic_task_mapping",
      "execution_date": "2023-07-09T10:00:00.00+00:00",
      "key": "some_key",
      "map_index": 0,
      "task_id": "mapped_task",
      "timestamp": "2023-07-09T10:19:02.567293+00:00"
    },
    {
      "dag_id": "test_dynamic_task_mapping",
      "execution_date": "2023-07-09T10:00:00.00+00:00",
      "key": "some_key",
      "map_index": 1,
      "task_id": "mapped_task",
      "timestamp": "2023-07-09T10:19:12.600518+00:00"
    },
    {
      "dag_id": "test_dynamic_task_mapping",
      "execution_date": "2023-07-09T10:00:00.00+00:00",
      "key": "some_key",
      "map_index": 2,
      "task_id": "mapped_task",
      "timestamp": "2023-07-09T10:19:22.609229+00:00"
    }
  ]
}

# get all xcom entries for a task instance with a specific map_index
curl -X 'GET' \
  'http://localhost:28080/api/v1/dags/test_dynamic_task_mapping/dagRuns/some_run_id/taskInstances/mapped_task/xcomEntries?map_index=1&limit=100' \
  -H 'accept: application/json'
{
  "total_entries": 2,
  "xcom_entries": [
    {
      "dag_id": "test_dynamic_task_mapping",
      "execution_date": "2023-07-09T10:00:00.00+00:00",
      "key": "return_value",
      "map_index": 1,
      "task_id": "mapped_task",
      "timestamp": "2023-07-09T10:19:12.624135+00:00"
    },
    {
      "dag_id": "test_dynamic_task_mapping",
      "execution_date": "2023-07-09T10:00:00.00+00:00",
      "key": "some_key",
      "map_index": 1,
      "task_id": "mapped_task",
      "timestamp": "2023-07-09T10:19:12.600518+00:00"
    }
  ]
}

# get all xcom entries for a task instance with a specific map_index and key
curl -X 'GET' \
  'http://localhost:28080/api/v1/dags/test_dynamic_task_mapping/dagRuns/some_run_id/taskInstances/mapped_task/xcomEntries?map_index=1&xcom_key=some_key&limit=100' \
  -H 'accept: application/json'
{
  "total_entries": 1,
  "xcom_entries": [
    {
      "dag_id": "test_dynamic_task_mapping",
      "execution_date": "2023-07-09T10:00:00.00+00:00",
      "key": "some_key",
      "map_index": 1,
      "task_id": "mapped_task",
      "timestamp": "2023-07-09T10:19:12.600518+00:00"
    }
  ]
}

And for the value of a single xcom entry:

# get xcom entry for a task instance
curl -X 'GET' \
  'http://localhost:28080/api/v1/dags/test_dynamic_task_mapping/dagRuns/some_run_id/taskInstances/simple_task/xcomEntries/return_value?deserialize=false' \
  -H 'accept: application/json'
{
  "dag_id": "test_dynamic_task_mapping",
  "execution_date": "2023-07-09T10:00:00.00+00:00",
  "key": "return_value",
  "map_index": -1,
  "task_id": "simple_task",
  "timestamp": "2023-07-09T10:18:51.030130+00:00",
  "value": "[1, 2, 3]"
}

# get xcom entry for a mapped task instance, by default there is no result because the default map_index is -1
curl -X 'GET' \
  'http://localhost:28080/api/v1/dags/test_dynamic_task_mapping/dagRuns/some_run_id/taskInstances/mapped_task/xcomEntries/return_value?deserialize=false' \
  -H 'accept: application/json'
{
  "detail": null,
  "status": 404,
  "title": "XCom entry not found",
  "type": "http://apache-airflow-docs.s3-website.eu-central-1.amazonaws.com/docs/apache-airflow/latest/stable-rest-api-ref.html#section/Errors/NotFound"
}

# get xcom entry for a mapped task instance with a specific map_index
curl -X 'GET' \
  'http://localhost:28080/api/v1/dags/test_dynamic_task_mapping/dagRuns/some_run_id/taskInstances/mapped_task/xcomEntries/return_value?map_index=0&deserialize=false' \
  -H 'accept: application/json'
{
  "dag_id": "test_dynamic_task_mapping",
  "execution_date": "2023-07-09T10:00:00.00+00:00",
  "key": "return_value",
  "map_index": 0,
  "task_id": "mapped_task",
  "timestamp": "2023-07-09T10:19:02.578137+00:00",
  "value": "2"
}

---

^ Add meaningful description above

Read the Pull Request Guidelines for more information.
In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in a newsfragment file, named {pr_number}.significant.rst or {issue_number}.significant.rst, in newsfragments.

[potiuk]

It does seem like a very reasonable change.