Deprecate (and eventually remove) `tp_is_gc`

Feature or enhancement

Proposal:

The existence of tp_is_gc slows down and complicates allocation, deallocation and garbage collection.

But there is no need for it, as statically allocated objects can be marked as immortal as will be ignored by the GC.
I doubt there is much third-party code that uses it, if any.

We should deprecate it, and then remove it.

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:

No response

まず CPython における tp_is_gc の定義とすべての使用箇所を特定し、次に静的に割り当てられたオブジェクトがどのように immortal としてマークされ、ガベージコレクターによって処理されるかを調査します。非推奨化と最終的な削除の範囲を、サードパーティ拡張に対する互換性への影響も含めて明らかにします。提案された置き換えが検証され、非推奨化または削除が一貫して実装されれば完了です。