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/buttontable.lua

@@ -56,8 +56,8 @@ function ButtonTable:init()
                 callback = btn_entry.callback,
                 hold_callback = btn_entry.hold_callback,
                 vsync = btn_entry.vsync,
-                width = (self.width - sizer_space)/column_cnt,
-                max_width = (self.width - sizer_space)/column_cnt - 2*self.sep_width - 2*self.padding,
+                width = math.ceil((self.width - sizer_space)/column_cnt),
+                max_width = math.ceil((self.width - sizer_space)/column_cnt - 2*self.sep_width - 2*self.padding),
                 bordersize = 0,
                 margin = 0,
                 padding = Size.padding.buttontable, -- a bit taller than standalone buttons, for easier tap
@@ -88,7 +88,7 @@ function ButtonTable:init()
             self:addHorizontalSep(true, true, true)
         end
         if column_cnt > 0 then
-            --Only add line that are not separator to the focusmanager
+            -- Only add lines that are not separator to the focusmanager
             table.insert(self.buttons_layout, buttons_layout_line)
         end
     end -- end for each button line