feat(api) allow always hiding remote videos for 1-1 calls

config.js

     // enableClosePage: false,
 
     // Disable hiding of remote thumbnails when in a 1-on-1 conference call.
-    // disable1On1Mode: false,
+    // Setting this to null, will also disable showing the remote videos
+    // when the toolbar is shown on mouse movements
+    // disable1On1Mode: null | false | true,
 
     // Default language for the user interface.
     // defaultLanguage: 'en',

react/features/filmstrip/functions.web.js

     // in the filmstrip.
     const participantCount = getParticipantCountWithFake(state);
     let pinnedParticipant;
+    const { disable1On1Mode } = state['features/base/config'];
 
     return Boolean(
         participantCount > 2
             // Always show the filmstrip when there is another participant to
             // show and the  local video is pinned, or the toolbar is displayed.
             || (participantCount > 1
+                && disable1On1Mode !== null
                 && (state['features/toolbox'].visible
                     || ((pinnedParticipant = getPinnedParticipant(state))
                         && pinnedParticipant.local)))
 
-            || state['features/base/config'].disable1On1Mode);
+            || disable1On1Mode);
 }
 
 /**