[dev-launcher] Expose method to determine if you are running in a development build (#16486)

# Why

Closes ENG-2627.

# How

Checks if the `EXDevLauncher` module exists. It will only exist in

[dev-launcher] Expose method to determine if you are running in a development build (#16486)

# Why

Closes ENG-2627.

# How

Checks if the `EXDevLauncher` module exists. It will only exist in the development build.

# Test Plan

Run:
```js
export default function App() {
return (
<View style={styles.container}>
<Text>{ DevClient. isDevelopmentBuild() }</Text>
<StatusBar style="auto" />
</View>
);
}
```
inside:
- development build ✅
- expo go ✅

show more ...