Support supportsMethod in FlipperPlugin

Summary: `supportsMethod` wasn't implemented in the new sandy APIs so far, but is needed for D24108772

Reviewed By: cekkaewnumchai

Differential Revision: D24109496

fbshipit-source-id: 694344b423c1805baa193e4f2e1ad5f28483378b

desktop/flipper-plugin/src/test-utils/test-utils.tsx

@@ -43,6 +43,8 @@ interface StartPluginOptions {
   initialState?: Record<string, any>;
   isArchived?: boolean;
   isBackgroundPlugin?: boolean;
+  /** Provide a set of unsupported methods to simulate older clients that don't support certain methods yet */
+  unsupportedMethods?: string[];
 }
 
 type ExtractClientType<Module extends FlipperPluginModule<any>> = Parameters<
@@ -195,6 +197,9 @@ export function startPlugin<Module extends FlipperPluginModule<any>>(
     ): Promise<Object> {
       return sendStub(method, params);
     },
+    async supportsMethod(_api: string, method: string) {
+      return !options?.unsupportedMethods?.includes(method);
+    },
   };
 
   const pluginInstance = new SandyPluginInstance(