DB migration: TaskInstance tables from execution_date to run_id

[kaxil]

Create a migration for the following tables to use dag_run.run_id instead of execution_date. Remove execution_date from the primary_key too.

• TaskInstance Change TaskInstance and TaskReschedule PK from execution_date to run_id #17719
• TaskFail
• TaskReschedule Change TaskInstance and TaskReschedule PK from execution_date to run_id #17719
• RenderedTaskInstanceFields

Use SQLAlchemy's Association proxy (https://docs.sqlalchemy.org/en/13/orm/extensions/associationproxy.html) for keeping backwards compatibility for execution_date.

As part of this, also replace the usage of TI.execution_date to TI.run_id in the entire codebase.

Add a check *BEFORE any migrations are run to ensure that there are no missing DagRuns for a TaskInstance and vice-versa, and that a user is not left with a DB version "part-way" between two Airflow versions.