Revert "Migrate Collapse/Open Resource Tree to React (#733)" (#792)

This reverts commit d7c62ac7f1.

less/documentDB.less

@@ -2099,7 +2099,7 @@ a:link {
   display: flex;
   flex: 1 1 auto;
   overflow-x: auto;
-  overflow-y: hidden;
+  overflow-y: auto;
   height: 100%;
 }
 
@@ -3085,7 +3085,3 @@ settings-pane {
     padding-left: @SmallSpace;
   }
 }
-.hiddenMain {
-  visibility: hidden;
-  height: 0px;
-}

less/tree.less

@@ -3,7 +3,6 @@
 
 .resourceTree {
     height: 100%;
-    width: 20%;
     flex: 0 0 auto;
     .main {
         height: 100%;