Restore get_previous_dagrun functionality for task context

[kaxil]

Add get_previous_dagrun method to RuntimeTaskInstance to replace the removed DagRun.get_previous_dagrun() method from Airflow 2.x. This enables users to access previous DAG run information from task context for conditional logic like notifications on state changes.

Changes:

• Add GetPreviousDagRun message and PreviousDagRunResult response in comms
• Add get_previous_dagrun instance method to RuntimeTaskInstance
• Add /dag-runs/{dag_id}/previous API endpoint with optional state filtering
• Add get_previous method to DagRunOperations API client
• Update supervisor to handle GetPreviousDagRun messages

ToDo:

• Add Cadwyn migration
• Remove defaults when sending serialized object to buffer

Usage:

defmy_task(context):
ti=context["ti"]
previous_run=ti.get_previous_dagrun()
ifprevious_run:
# Access previous run metadataprint(f"Previous run: {previous_run.dag_run.run_id}")

or

@dagdefa_dag():
@task(task_id="print_the_context")defprint_context(**kwargs):
ctx=get_current_context()
dr=ctx["dag_run"]
print("Current dag run:")
pprint(dr)
print()
print("Getting prev dag run...")
gpd=ctx["ti"].get_previous_dagrun()
print("Previous dag run:")
pprint(gpd)
run_this=print_context()

Fixes#53628

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[amoghrajesh]

Just a comment, looks good otherwise!