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/apps/reader/modules/readerbookmark.lua

@@ -182,7 +182,7 @@ function ReaderBookmark:onToggleBookmark()
         pn_or_xp = self.ui.document:getXPointer()
     end
     self:toggleBookmark(pn_or_xp)
-    self.view.footer:onUpdateFooter(true)
+    self.view.footer:onUpdateFooter(self.view.footer_visible)
     self.ui:handleEvent(Event:new("SetDogearVisibility",
                                   not self.view.dogear_visible))
     UIManager:setDirty(self.view.dialog, "ui")
@@ -426,7 +426,7 @@ function ReaderBookmark:addBookmark(item)
         end
     end
     table.insert(self.bookmarks, _middle + direction, item)
-    self.view.footer:onUpdateFooter(true)
+    self.view.footer:onUpdateFooter(self.view.footer_visible)
 end
 
 -- binary search of sorted bookmarks
@@ -470,7 +470,7 @@ function ReaderBookmark:removeBookmark(item)
         local v = self.bookmarks[_middle]
         if item.datetime == v.datetime and item.page == v.page then
             table.remove(self.bookmarks, _middle)
-            self.view.footer:onUpdateFooter(true)
+            self.view.footer:onUpdateFooter(self.view.footer_visible)
             return
         elseif self:isBookmarkInPageOrder(item, v) then
             _end = _middle - 1
@@ -487,7 +487,7 @@ function ReaderBookmark:removeBookmark(item)
         local v = self.bookmarks[i]
         if item.datetime == v.datetime and item.page == v.page then
             table.remove(self.bookmarks, i)
-            self.view.footer:onUpdateFooter(true)
+            self.view.footer:onUpdateFooter(self.view.footer_visible)
             return
         end
     end