* Fix merge options leaks to next screen in stack

* Rename mergeChild:options to mergeChildOptions:options:

* Rename mergeChildOptions:options: to mergeChildOptions:child:

This commit adds support to update props of screen or custom button/title via the mergeOptions api.

```js
Navigation.mergeOptions('myComponentId', {
  passProps: {
    text: 'new value'
  }
});
```

* Fix button with react component doesn't get unmounted

* Test e2e only on iOS

When defaultOptions are set after setRoot has been called presenters need to receive the default options as well,
otherwise the outdated default options are regarded.
Fixes #5395

* Cleanup and reorganise playground app

* Separated tests into three categories
  1. Layouts - layout specific tests and feature showcase
  2. Options - options related tests; interactions between static and dynamic options, merge options etc
  3. Navigation - general navigation features; Orientation handling, events, Overlay etc

* Fixed a few Android bugs
  1. testID wasn’t applied on TopBar react buttons
  2. static options were disregarded when creating initial BottomTab options
  3. Trying to open a none existent SideMenu would result in a crash

* Fix e2e tests

* Fix lint

* Few fixes + split push from SideMenu test into two tests

* Fixes e2e