Kobo: Refactor various aspects of the Kaleido/MTK support (#12221)

* UIManager: Let the fb backend deal with Kaleido wfm promotion. This fixes a number of quirks that poisoned the refresh queue with spurious full-screen refreshes. See https://github.com/koreader/koreader-base/pull/1865 for more details.
* This also means we now disable Kaleido waveform modes when color rendering is disabled (remember to trash your thumbnail cache if you don't want to mix color w/ grayscale thumbnails, though).
* UIManager: Merge refreshes that share an edge, because that was driving me nuts (and would have most likely been merged by the kernel anyway). A perfect test-case is the FM, which trips two separate refreshes because of its title bar.
* ReaderFlipping: Use sensible dimensions, so that we only refresh the icon's region.
* ReaderBookmark: Only refresh the dogear instead of the whole page when toggling bookmarks.
* NetworkSetting: Make it a real boy, so it consistently refreshes properly on dismiss instead of relying on UIManager saving the day.
* Kobo: Aggressively prevent *both* suspend & standby while MTK devices are plugged-in, as both will horribly implode the kernel (we previously only prevent standby while charging).
* Kobo: Switch to 8bpp on B&W MTK devices (or when color rendering is disabled on Kaleido panels).

frontend/apps/reader/modules/readerview.lua

@@ -264,10 +264,6 @@ function ReaderView:paintTo(bb, x, y)
     if self.ui.paging then
         if self.document.hw_dithering then
             self.dialog.dithered = true
-            -- Assume we're going to be showing colorful stuff on kaleido panels...
-            if Device:hasKaleidoWfm() then
-                UIManager:setDirty(nil, "color")
-            end
         end
     else
         -- Whereas for CRe,
@@ -278,15 +274,14 @@ function ReaderView:paintTo(bb, x, y)
         -- Which is why we remember the stats of the *previous* page.
         self.img_count, self.img_coverage = img_count, img_coverage
         if img_coverage >= 0.075 or coverage_diff >= 0.075 then
-            self.dialog.dithered = true
+            -- Request dithering on the actual page with image content
+            if img_coverage >= 0.075 then
+                self.dialog.dithered = true
+            end
             -- Request a flashing update while we're at it, but only if it's the first time we're painting it
             if self.state.drawn == false and G_reader_settings:nilOrTrue("refresh_on_pages_with_images") then
                 UIManager:setDirty(nil, "full")
             end
-            -- On Kaleido panels, we'll want to use GCC16 on the actual image, always...
-            if Device:hasKaleidoWfm() and img_coverage >= 0.075 then
-                UIManager:setDirty(nil, "color")
-            end
         end
         self.state.drawn = true
     end