List active *runtime* sessions through the SDK

**Is your feature request related to a problem? Please describe.**
I'm frustrated there isn't a way to list active runtime sessions programatically.

I'm under the impression that neither `idle_runtime_session_timeout=60` nor `stop_runtime_session` are closing sessions since my memory consumption is not going to 0 - so have an API/SDK function for finding and closing these sessions would help.

**Describe the solution you'd like**
I'd like to list active runtime sessions **(not memory sessions)** through the SDK so I can kill then using `stop_runtime_session` depending on their state.

**Describe alternatives you've considered**
I've tried looking for APIs or documentation on how to have access to runtime session, but found nothing about it.

**Additional context**
Add any other context or screenshots about the feature request here.

ファイルやテストは指定されていません。まず stop_runtime_session の SDK エントリポイントと基盤となる runtime service API を確認し、次にアクティブな runtime セッションをメモリセッションとは別に列挙できるかを検証します。セッションの停止に適した状態情報とともに、その一覧を SDK 経由で公開できれば完了です。

索引モデルが issue の本文から書いたものです。