[SDK] Standardize code style using YAPF and docformatter.

[chensun]

Currently, the KFP SDK code isn’t formatted consistently. One noticeable inconsistency is that some files have 2-space indentation (conforms to Google internal style) while others have 4-space indentation (conforms to PEP8 and Google Python Style Guide). To have a clean, consistent code base, we should pick a formatting style and stick with it.

Based some evaluation of both Google's internal style and the public Google Python Style Guide, we decided on the following YAPF configuration:

[style]
based_on_style = yapf
indent_width = 4
split_before_named_assigns = true
column_limit = 80

The new style config only applies to KFP SDK code. While for components, component authors can pick their own style.

/area sdk

/cc @neuromage @ji-yaqi /cc @IronPan @SinaChavoshi /cc @Bobgy

[chensun]

Tracking action items:

• [x] https://github.com/kubeflow/pipelines/pull/6467
• [x] https://github.com/kubeflow/pipelines/pull/6501
• [ ] TODO: Check formatting in CI.

[neuromage]

/lgtm

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[rimolive]

Closing this issue. No activity for more than a year.

/close

[google-oss-prow[bot]]

@rimolive: Closing this issue.

In response to [this](https://github.com/kubeflow/pipelines/issues/6500#issuecomment-2021376045): >Closing this issue. No activity for more than a year. > >/close Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.