Tame some ButtonTable users into re-using Buttontable instances if possible (#7166)

* QuickDictLookup, ImageViewer, NumberPicker: Smarter `update` that will re-use most of the widget's layout instead of re-instantiating all the things.
* SpinWidget/DoubleSpinWidget: The NumberPicker change above renders a hack to preserve alpha on these widgets almost unnecessary. Also fixed said hack to also apply to the center, value button.

* Button: Don't re-instantiate the frame in setText/setIcon when unnecessary (e.g., no change at all, or no layout change).
* Button: Add a refresh method that repaints and refreshes a *specific* Button (provided it's been painted once) all on its lonesome.

* ConfigDialog: Free everything that's going to be re-instatiated on update
 
* A few more post #7118 fixes:
  * SkimTo: Always flag the chapter nav buttons as vsync
  * Button: Fix the highlight on rounded buttons when vsync is enabled (e.g., it's now entirely visible, instead of showing a weird inverted corner glitch).
  * Some more heuristic tweaks in Menu/TouchMenu/Button/IconButton
* ButtonTable: fix the annoying rounding issue I'd noticed in #7054 ;).

* Enable dithering in TextBoxWidget (e.g., in the Wikipedia full view). This involved moving the HW dithering align fixup to base, where it always ought to have been ;).

* Switch a few widgets that were using "partial" on close to "ui", or, more rarely, "flashui". The intent being to limit "partial" purely to the Reader, because it has a latency cost when mixed with other refreshes, which happens often enough in UI ;).

* Minor documentation tweaks around UIManager's `setDirty` to reflect that change.

* ReaderFooter: Force a footer repaint on resume if it is visible (otherwise, just update it).
* ReaderBookmark: In the same vein, don't repaint an invisible footer on bookmark count changes.

frontend/ui/widget/touchmenu.lua

@@ -186,9 +186,16 @@ function TouchMenuItem:onTapSelect(arg, ges)
                 return true
             end
 
-            -- If the callback opened the Virtual Keyboard, we're done
+            -- If the callback opened the Virtual Keyboard, it gets trickier
             -- (this is for TextEditor, Terminal & co)
             if top_widget == "VirtualKeyboard" then
+                -- Unfortunately, we can't really tell full-screen widgets (e.g., TextEditor, Terminal) apart from
+                -- stuff that might just pop the keyboard for a TextInput box...
+                -- So, a full fenced redraw it is...
+                UIManager:waitForVSync()
+                UIManager:setDirty(self.show_parent, function()
+                    return "ui", highlight_dimen
+                end)
                 return true
             end