Ensure hooks and plugins are included in the mock runtime api

[knolleary]

Alternative fix to #73 - rather than stub it, expose the real internal plugin api.

[knolleary]

Initial testing suggests more is needed. Parking for now - will merge/release with #73 to unblock some other work that is happening and come back to this another day.

[joepavitt]

Just tried this locally, and this._RED.plugins is undefined in the index.js

[joepavitt]

Mentioned that it should have been this._RED.runtime.plugins

Even with this, we then see different behaviour to core:

Test Helper:

RED.plugins.getByType('node-red-dashboard-2') returns Promise { [ ] }

Node-RED Core:

RED.plugins.getByType('node-red-dashboard-2') returns []

[knolleary]

@joepavitt that is odd. Can't see anything async in either code path that would result in a promise.