text: Title: execution options param in ORM session hardcoded to immutable dict
  Body: ### Discussed in https://github.com/sqlalchemy/sqlalchemy/discussions/10181
  
  ```py
  from sqlalchemy.orm import Session
  
  session: Session
  
  session.connection(
      execution_options={"isolation_level": "REPEATABLE READ"}
  )
  ```
  
  ```
  $ mypy test3.py 
  test3.py:6: error: Argument "execution_options" to "connection" of "Session" has incompatible type "dict[str, str]"; expected "immutabledict[str, Any] | None"  [arg-type]
  Found 1 error in 1 file (checked 1 source file)
  
  ```