[React Native] Remove eventTypes from ReactNativeBridgeEventPlugin

[rickhanlonii]

Overview

This PR fixes an issue with switching between paper and fabric in React Native.

Explanation

On first initialization of React Native, ReactNativeBridgeEventPlugin.eventTypes is empty because view configs are lazily loaded. This means that the EventPluginRegistry does not run checks on events, and does not error when registering here.

If there is a second initialization (e.g. loading the fabric bundle after the paper bundle), then the eventTypes may be populated with host component events from view configs loaded at runtime.

This means that the EventPluginRegistry can error when registering the plugin if there are colliding registration names, even though these events were already in use.

This change allows the EventPluginRegistry to perform the same on initial load between all of the bundles by forcing the eventTypes to an empty object.

Justification

From the EventPluginHub doc comments, eventTypes are optional:

`eventTypes` {object}
      Optional, plugins that fire events must publish a mapping of registration
      names that are used to register listeners. Values of this mapping must
      be objects that contain `registrationName` or `phasedRegistrationNames`.

For ReactNative, we register our own top level listeners in our native host components so there is no need to register them in the EventPluginHub.

Testing

See https://fburl.com/diff/5l6zql59 for test plan.

[rickhanlonii]

Note: even though the docstring says this is optional, the flowtype disagress

[rickhanlonii]

Note that the EventPluginRegistry seems to be checking registration names for use in registrationNameModules, which appears to only be used in react-dom

[sizebot]

No significant bundle size changes to report.

Generated by 🚫 dangerJS

[gaearon]

Not super familiar with this but if they're already lazy loaded then this looks fine to me

[cpojer]

👍