Create first test flow (#45574)

Summary:
## Context
Running manual tests when preparing a release, it's time consuming.
We have to do the cherry picks, wait for CI to finish, and then manually test 8 configurations.

Maestro is a tool that allow us to run E2E tests automatically, and we can wire it to CI.

## Change
Add a test flow for RNTester

## Changelog:
[Internal] - Exploration to integrate maestro

Pull Request resolved: https://github.com/facebook/react-native/pull/45574

Test Plan: GHA

Reviewed By: blakef

Differential Revision: D60282147

Pulled By: cipolleschi

fbshipit-source-id: 4ecba84f0b2c7186de2bb9938043e73a0bd9a6bd

packages/rn-tester/.maestro/start.yml

@@ -0,0 +1,11 @@
+appId: ${APP_ID} # iOS: com.meta.RNTester.localDevelopment | Android: com.facebook.react.uiapp
+---
+- launchApp
+- assertVisible: "Components"
+- scrollUntilVisible:
+    element:
+      id: "Modal"
+    direction: DOWN
+    speed: 60
+- tapOn:
+    id: "Modal"