Improve importlib backports-upstream integration

The current status-quo when it comes to the development integration/synchronization between the importlib backports and the CPython upstream isn't optimal.

Before anything else, I must properly acknowledge @jaraco's monumental and tireless effort on maintaining the importlib backports, and handling the complex synchronization with the CPython upstream, not to mention the continued development of these modules. It has been instrumental to get things to the state they are today, and none of the issues discussed in this thread should reflect negatively on him, but rather our failure to ensure these projects got the resources they need — a far too common tale in open-source.

Here are some issues I think we should improve:

• Synchronization process — even though @jaraco has left comments in some PRs describing his workflow, there's no properly documented process
• Authorship stripping — the current way changes are synced in and from the backports strip commit authorship
• Documentation fragmentation, resulting in a sub-optimal documentation
  • Eg. importlib.metadata.Distribution, and other classes, do not document their attributes (I regularly have to resort to the source code)
• CLA enforcement — the backports do not enforce the CLA
• Segmented development workflow — issues and changes happen in both places
• Source history — the current way changes are synced in and from the backports strip commit history

cc @python/importlib-team

该 issue 未指定任何文件或测试。首先审查 importlib backports 和 CPython upstream synchronization workflow，包括作者信息、源代码历史、CLA 执行情况以及文档方面的问题。要视为完成，需要对集成流程达成一项改进共识，但该 issue 未定义具体的实现方案或验收标准。