fix: share 'LuIntentEditor' widget across recognizers

[yeze322]

Description

closes #4167

According to design, the <LuIntentEditor /> widget will be applied to not only LuisRecognizer and CrossTrainedRecognizer but the PVARecognizer. Previously, sharing widgets between recognizer uischemas was implemented in a hack way, in which a widget is copied manually from one recognizer to another.

This PR solves the problem by registering and sharing widgets via the widgets object in the PluginConfig as Flow widgets did. All recognizer-related widgets will be put under the widgets.recognizer filed of PluginConfig.

Now, the definition of PluginConfig look like this:

export interface PluginConfig {
  uiSchema?: UISchema;
  widgets?: UIWidgets;
}

export type UIWidgets = {
  flow?: FlowEditorWidgetMap;
  recognizer?: { [name: string]: FieldWidget };
};

In PVA scenario, PVARecognizer can consume the widget LuIntentEditor as below @tonyanziano.

{
  "Microsoft.PVARecgonizer": {
    ...,
    "intentEditor": "LuIntentEditor"
  }
}

PVA Remaining problems:

• Need a solution to retrive the recognizer's .lu file via recognizer json.

Task Item

Screenshots

Here is the LuIntentEditor

[coveralls]

Coverage increased (+0.004%) to 56.026% when pulling 4aa9cbe on yeze322:uiwidgets/recognizer into d5fdd02 on microsoft:main.