feat)rn,sdk) introduce a "ready to close" event

This event is the event host applications need to listen to for knowing when to
dispose the SDK from now on.

Since the introduction of breakout rooms it's possible that we navigate from one
meeting to another, so there will be several conference join / terminations.

In addition, local track destruction is now moved to SET_ROOM when there is no
room, aka, we are going back to the welcome page or to the black page.

react/features/overlay/components/native/LoadConfigOverlay.js

@@ -1,16 +1,14 @@
 // @flow
 
-import React, { Component } from 'react';
+import React, { PureComponent } from 'react';
 import { SafeAreaView, Text, View } from 'react-native';
 
-import { ColorSchemeRegistry } from '../../../base/color-scheme';
 import { translate } from '../../../base/i18n';
 import { LoadingIndicator } from '../../../base/react';
-import { connect } from '../../../base/redux';
 import { StyleType } from '../../../base/styles';
 
 import OverlayFrame from './OverlayFrame';
-import styles from './styles';
+import styles, { TEXT_COLOR } from './styles';
 
 type Props = {
 
@@ -29,7 +27,7 @@ type Props = {
  * Implements an overlay to tell the user that there is an operation in progress in the background during connect
  * so then the app doesn't seem hung.
  */
-class LoadConfigOverlay extends Component<Props> {
+class LoadConfigOverlay extends PureComponent<Props> {
     /**
      * Determines whether this overlay needs to be rendered (according to a
      * specific redux state). Called by {@link OverlayContainer}.
@@ -49,25 +47,15 @@ class LoadConfigOverlay extends Component<Props> {
      * @returns {ReactElement}
      */
     render() {
-        const { _styles } = this.props;
-
         return (
             <OverlayFrame>
-                <View
-                    style = { [
-                        styles.loadingOverlayWrapper,
-                        _styles.loadingOverlayWrapper
-                    ] }>
+                <View style = { styles.loadingOverlayWrapper }>
                     <SafeAreaView>
                         <LoadingIndicator
-                            color = { _styles.indicatorColor }
+                            color = { TEXT_COLOR }
                             size = 'large'
                             style = { styles.connectIndicator } />
-                        <Text
-                            style = { [
-                                styles.loadingOverlayText,
-                                _styles.loadingOverlayText
-                            ] }>
+                        <Text style = { styles.loadingOverlayText }>
                             { this.props.t('connectingOverlay.joiningRoom') }
                         </Text>
                     </SafeAreaView>
@@ -77,18 +65,5 @@ class LoadConfigOverlay extends Component<Props> {
     }
 }
 
-/**
- * Maps part of the Redux state to the props of this component.
- *
- * @param {Object} state - The Redux state.
- * @returns {{
- *     _styles: StyleType
- * }}
- */
-function _mapStateToProps(state) {
-    return {
-        _styles: ColorSchemeRegistry.get(state, 'LoadConfigOverlay')
-    };
-}
 
-export default translate(connect(_mapStateToProps)(LoadConfigOverlay));
+export default translate(LoadConfigOverlay);