Close serialized webview when another view already exists

When deserializing a webview, it could happen that a view was already
manually opened by the user before the webview was deserialized. This
would result in duplicate webview tabs, which is not supported by the
manager.

This will close the webview that is being deserialized and focus on the
existing view. This should ensure that we never have duplicate loaded
webview tabs. There could still be duplicate webview tabs if there are
non-deserialized tabs, but once it is opened it should be closed
automatically.

Author: koesie10

extensions/ql-vscode/src/remote-queries/variant-analysis-view-manager.ts

@@ -13,6 +13,7 @@ export interface VariantAnalysisViewManager<
 > {
   registerView(view: T): void;
   unregisterView(view: T): void;
+  getView(variantAnalysisId: number): T | undefined;
 
   getVariantAnalysis(
     variantAnalysisId: number,

extensions/ql-vscode/src/remote-queries/variant-analysis-view-serializer.ts

@@ -38,6 +38,15 @@ export class VariantAnalysisViewSerializer implements WebviewPanelSerializer {
 
     const manager = await this.waitForExtensionFullyLoaded();
 
+    const existingView = manager.getView(
+      variantAnalysisState.variantAnalysisId,
+    );
+    if (existingView) {
+      await existingView.openView();
+      webviewPanel.dispose();
+      return;
+    }
+
     const view = new VariantAnalysisView(
       this.ctx,
       variantAnalysisState.variantAnalysisId,