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:

def my_task(context):
    ti = context["ti"]
    previous_run = ti.get_previous_dagrun()
    if previous_run:
        # Access previous run metadata
        print(f"Previous run: {previous_run.dag_run.run_id}")

or

@dag
def a_dag():
    @task(task_id="print_the_context")
    def print_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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