Consider some way of serializing open projects in tsserver, potentially leveraging `.tsbuildinfo` files

One thing that users often hit is that file navigation might trigger opening an entire project. Opening an entire project involves

1. File loading
2. Scanning/parsing
3. Resolving dependencies
4. Keep repeating file loading on dependencies until no new files are found

This is a lot of work! If a user jumps back and forth from this file, it can re-trigger this work even if nothing has changed!

A .tsbuildinfo file is used to save time on cold compiler invocations doing this exact set of work, and to reduce work when something actually has changed. It would be interesting to see whether generating a .tsbuildinfo file after project loads could help cut down on this work.

まず、tsserver がプロジェクトを開く方法と、.tsbuildinfo ファイルが生成・利用される方法を調査します。ファイルが変更されていない場合のプロジェクトの繰り返し読み込みを比較し、動作を変更せずにシリアライゼーションによってその作業を削減できるかを定義します。合意された設計があり、変更されていないプロジェクトで不要な読み込み、解析、依存関係の解決を回避できることを示す証拠が得られれば完了です。