Data: Add RegistryConsumer export (#9042)

The plugin code relies on the RegistryProvider to be able to add
functionality to the registry. `withSelect` uses the RegistryConsumer,
but code outside of `@wordpress/data` can't access this modified
registry at all (even though it can create it!).
This solves the incongruence by simply exporting RegistryConsumer as
well.

packages/data/src/index.js

@@ -11,7 +11,7 @@ import * as plugins from './plugins';
 
 export { default as withSelect } from './components/with-select';
 export { default as withDispatch } from './components/with-dispatch';
-export { default as RegistryProvider } from './components/registry-provider';
+export { default as RegistryProvider, RegistryConsumer } from './components/registry-provider';
 export { createRegistry } from './registry';
 export {
 	withRehydration,