Make project import interactive

Right now, importing Java projects is happening at startup. I am aware that there is the "interactive" mode, but all that allows me to do is to veto the import of the projects. (If I select "later", how do I later import the projects? There seems to be no "Import Projects" command 🤷 )

Let's consider making the import more interactive by

• allow the user to pick which directories will be imported
• allow the user to select which import will import a directory is two or more want to import a given directory
• allow importers to ask the user to fix problems while importing (think "no compatible Java version" could be fixed by selecting a JDK directory).

In order to implement something like this, we'd have to move control of the import process to the vscode-java side instead of handling import in the language server. That would also alllow us to give more precise feedback if something goes wrong with the import. IMO.

まず、起動時のインポートフロー、既存のインタラクティブモード、VS Code拡張機能と言語サーバーの境界を追跡します。ユーザーがディレクトリとインポーターを選択し、インポーターの問題を解決し、後からインポートをトリガーする方法を定義します。これらのインタラクションが、起動時にのみ行われるインポートに依存せず、正確なフィードバックを提供できれば完了です。