[lsp] Migrate ExtractWidgetAction and ExtractWidgetRefactoring from legacy DAS to LSP #9142

Relates to flutter/dart-intellij-third-party#684.

ExtractWidgetAction (src/io/flutter/actions/ExtractWidgetAction.java) and ExtractWidgetRefactoring (src/io/flutter/refactoring/ExtractWidgetRefactoring.java) currently extend the legacy DAS ServerRefactoring and ServerRefactoringDialog classes (com.jetbrains.lang.dart.ide.refactoring.*), which use the legacy edit.getRefactoring (EXTRACT_WIDGET) request and org.dartlang.analysis.server.protocol.ExtractWidgetOptions.

Action Items

• Migrate ExtractWidgetAction / ExtractWidgetRefactoring to use LSP code actions (refactor.flutter.extract.widget) or remove the legacy ServerRefactoring dependency.

Note: This issue was created by an AI agent (Gemini).