Change TodoController in Todo/TodoList examples to the one generated by `lb4 controller`

[shimks]

Description / Steps to reproduce / Feature proposal

To make the tutorial process streamline, we should go from manually defining the controller methods to have it be automatically generated from the CLI.

Acceptance Criteria

• remove the current todo.controller.ts and replace it with the one generated by the CLI
  • replace the tests as well
• address the changes in the tutorial as well
  • find a way to keep the useful information in https://loopback.io/doc/en/lb4/todo-tutorial-controller.html or remove them entirely

[dhmlau]

@shimks , looks like we've modified this tutorial. Could you please check if this ticket still valid? Thanks.

[shimks]

@dhmlau Could you specify what the modification was?

[dhmlau]

it looks like that page still needs to be updated.

[dhmlau]

Marking it as LB4 GA p1 item because i think we should have the docs fixed.
@bajtos , feel free to modify if you disagree. Thanks.

[dhmlau]

@b-admike , i think this goes with the QuickLab you're working on.