Add WinMagic Subquery Decorrelation

Some correlated scalar subqueries repeatedly access tables that are already referenced by the outer query block, which can lead to unnecessary execution overhead.
Add WinMagic optimization to decorrelate eligible correlated scalar subqueries using window functions. This optimization reduces redundant access to tables shared by the outer query and subquery, allowing supported queries to be transformed into a window aggregation plan for better execution performance.

まず、相関スカラーサブクエリ用のオプティマイザのエントリポイントと、既存のウィンドウ集約変換を特定します。代表的な適格クエリで動作を検証します。完了の条件は、サポート対象の相関スカラーサブクエリが結果を変更せずにウィンドウ集約プランへ非相関化されることです。