EXP-1767 WIP Received Items panel state does not persist between sessions

ensure that layout stack has updated its layout before manually resizing one of its elements
(which was causing the manual resize to be stomped on by the newly triggered layout update)
made layout stack animation occur even when layout stack not visible (inventory will appear in proper open/closed state)
LLView::setShape() now only calls handleReshape() when dimensions change
removed extraneous calls to LLLayoutStack::updateClass() so that it should be called only
once per frame now, allowing it to limit animation updates to layout stacks to one per frame.
fixed rendering glitches arising from reshaping LLFolderView while in the middle of its draw() method