Block public access for functions [AWS account level]

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**Description**
Allow customers to write policies to block public access for all functions in an account. Customers can specify at the account level whether to block the attachment of new policies that would allow public access and/or restrict access to functions that are currently publicly accessible. These controls will enable you to block new public policies form being attached to any function in an account without impacting functions that are currently publicly accessible.

issue では、ファイル、テスト、エントリポイントが特定されていません。まず、アカウントレベルの AWS Lambda ポリシー制御と、提案されている両方の動作が必要かどうかを明確にします。完了の条件は、顧客がパブリックアクセスを許可する新しいポリシーをブロックでき、すでにパブリックにアクセス可能な関数をオプションで制限できることです。

索引モデルが issue の本文から書いたものです。