Allowing task_group Sensor in ExternalTaskSensor

[pateash]

closes: #14563
related: #14640

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Hi All,

This PR proposes to allow users to provide external_task_group_id in ExternalTaskSensor to make tasks on a DAG wait for another task_group on a different DAG for a specific execution_date.
we can also provide options to set if the Task on a remote DAG succeeded or failed via allowed_states and failed_states parameters.

[pateash]

cases

1. group1_sensor -> wait for task_group from external dag which exists and succeeded ( as per allowed_states )
2. group2_sensor- > wait for task_group from external dag which doesn't exists ( wait till timeout )
3. group2_sensor_check_enabled -> wait for task_group from external dag which doesn't exists and with check_enabled=True ( fail with error )

[pateash]

Hi @eladkal, could you please take a look into this PR.

[uranusjr]

Since we are already allowing multiple task IDs, I wonder if we should just go directly with external_group_ids instead of just one single group. Someone’s going to ask for that sooner or later.

[pateash]

@uranusjr, we already allow multiple taskIds which I personally don't think a good idea, because it is not very transparent.

Although For TaskGroup, I think if someone want to depend on multiple of them, they must create different task sensors.

[eladkal]

LGTM