Fix image preview extension for remote

Fixes #81434

- Make image preview a ui exension

- Add logic so that `asWebviewUri` supports preserving the scheme of the requested resource. This is important as we know where to load the resource from

src/vs/workbench/api/common/shared/webview.ts

@@ -17,7 +17,13 @@ export function asWebviewUri(
 	resource: vscode.Uri,
 ): vscode.Uri {
 	const uri = initData.webviewResourceRoot
-		.replace('{{resource}}', resource.toString().replace(/^\S+?:/, ''))
+		// Make sure we preserve the scheme of the resource but convert it into a normal path segment
+		// The scheme is important as we need to know if we are requesting a local or a remote resource.
+		.replace('{{resource}}', resource.scheme + withoutScheme(resource))
 		.replace('{{uuid}}', uuid);
 	return URI.parse(uri);
 }
+
+function withoutScheme(resource: vscode.Uri): string {
+	return resource.toString().replace(/^\S+?:/, '');
+}