Make "TaskInstance" we send between executor and workers resilient to change (#48894)

This is a similar sort of change to #48888, but in that case the fix is API
versioning, here we can't make use of that approach as the the TI isn't sent
over the API  -- it's sent via the Executor to the worker.

So for now the best approach we have here is to allow extra, and be careful
when adding new fields to make sure it is version compatible.

This will need special handling in #48887 too.

Author: ashb

airflow-core/src/airflow/api_fastapi/execution_api/datamodels/taskinstance.py

@@ -230,7 +230,7 @@ class TIHeartbeatInfo(StrictBaseModel):
 
 # This model is not used in the API, but it is included in generated OpenAPI schema
 # for use in the client SDKs.
-class TaskInstance(StrictBaseModel):
+class TaskInstance(BaseModel):
     """Schema for TaskInstance model with minimal required fields needed for Runtime."""
 
     id: uuid.UUID

task-sdk/src/airflow/sdk/api/datamodels/_generated.py

@@ -350,9 +350,6 @@ class TaskInstance(BaseModel):
     Schema for TaskInstance model with minimal required fields needed for Runtime.
     """
 
-    model_config = ConfigDict(
-        extra="forbid",
-    )
     id: Annotated[UUID, Field(title="Id")]
     task_id: Annotated[str, Field(title="Task Id")]
     dag_id: Annotated[str, Field(title="Dag Id")]