detox.init() should not launch app

[rotemmiz]

Instead, let the users control when they want to launch the app for the first time.
This is useful when using mock servers, and a better control of when the app launches is needed.

So instead of :

before(async () => {
  await detox.init();
}

The equivalent will be:

before(async () => {
  await detox.init();
  await device.relaunchApp();
}

• Also add an example in the demo app and docs.

[LeoNatan]

This how Apple’s XCUITest works. The user has to explicitly launch the app.

Maybe we should consider having an application proxy class, like Apples: https://developer.apple.com/documentation/xctest/xcuiapplication?language=objc