[Enum] officially support `member.member` access and remove deprecation

[ethanfurman]

Due to performance concerns, and seeing some good examples of when member.member access makes sense, I'd like to remove the deprecation and instead officially support it.

Does anything special need to happen to approve this, or do I just update the docs, code, etc.? The current PR is here.

[gpshead]

additional context: this means closing python/cpython#95077 as "not planned".

[gpshead]

A few of us chatted: agreed, keep the member.member behavior instead of the deprecation.

Focusing on some mix of existing exposed enum API compatibility and enabling better performance seems like a great idea.