* [Doc] Update runner documents.

* update

* fix link

* update

* update

* Update import manner of Runner

Co-authored-by: Wenwei Zhang <40779233+ZwwWayne@users.noreply.github.com>

* Modify val_interval and val_begin to be the attributes of TrainLoop.

* update doc

* fix lint

* type hint

* Replace markdownlint with mdformat to avoid installing ruby

* fix circleci

* [Doc] Refine runner doc.

* resolve comments

* [Doc] Add runner tutorial.

* update

* add advanced doc

* refine and add flow chart

* update

* update