Use react-native-cli with the Android debugging fix

[hypest]

The recent upgrade to React Native 0.59 had a regression that made us lose the ability to properly debug the JS source code under Android.

This PR introduces a workaround by using the fixes version of the react-native-cli package, before it becomes available directly via a future React Native release.

Relevant tickets: facebook/react-native#23955, facebook/metro#380

To test:

0. Add a debugger; statement somewhere in the JS code. Good examples can be the block-holder.js module and the render() function in gutenberg/.../components/rich-text/index.native.js.
1. Run the demo app on Android
2. Enable the Remote JS debugging mode via the debug menu, and notice Chrome opening up to debug
3. Notice the debugger stopping at the debugger statements and properly showing the source file

[mkevins]

I tested this on Android emulator w/ Chromium 73.0. It works 🎉!

I was able to set debug lines directly in the Chromium debugger, as well as in code with the debugger statement. Also, the variable scopes and closures are correct.

[mkevins]

This is a great workaround until the fix is merged upstream.

Thanks @hypest !