[FEATURE] Sequencer admin contract to encapsulate keys (and namespace) within execution client state root

## Is your feature request related to a problem? Please describe.

Yes, we would like to encapsulate the public key of the sequencer within the state root of the execution client to avoid having to validate it independently for proving state transition and data availability.

Furthermore, this design lends itself to support key rotation for the sequencer software. Which is an issue independent of this, but it would be great to kill two birds with one stone.

## Describe the solution you'd like

Spoke with @tac0turtle about requesting the state root to include the sequencer's public key as well as the namespace it posts data to.

He mentioned that it could be possible to use existing staking contracts.

## Describe alternatives you've considered

Currently we verify the namespace and public key of the sequencer independently of the execution client state root. But ideally we can reduce it to only the state root if those fields are encapsulated within it.

## Additional context

n/a

issue にはファイル、テスト、エントリーポイントが特定されていません。まず、execution client state root が現在 sequencer namespace および public key とどのように関係しているかを確認し、次に既存の staking contracts でそれらのフィールドを表現できるかを調べてください。完了とは、state root が両方の値を提供でき、提案された検証変更をサポートする、合意済みの実装ができていることを意味します。

索引モデルが issue の本文から書いたものです。