Expand payload types for `email.message.Message.set_payload`

Feature or enhancement

Proposal:

While working on bug in PR #136071 we (me and @picnixz) discussed that set_payload of email.message.Message method could use list, str, bytes or handle buffer objects as payload to set.

For now it using duck type for objects with decode and encode methods. https://github.com/python/cpython/blob/main/Lib/email/message.py#L335-L353

I guess we need to decide necessary of it and if so the types that need to be support. Also update typing in typeshed for email.message.Message

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

#134759
#136071

まず、335～353 行付近の Lib/email/message.py と、#134759 および #136071 にリンクされている議論を読んでください。サポートされている payload 型を判断し、typeshed の email.message.Message の typing を更新してください。型に関する判断が解決され、ランタイムの動作とアノテーションの両方にそれが反映されれば完了です。