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).

reader.lua

@@ -202,14 +202,14 @@ if G_reader_settings:isTrue("color_rendering") and not Device:hasColorScreen() t
         text = _("Color rendering is mistakenly enabled on your grayscale device.\nThis will subtly break some features, and adversely affect performance."),
         cancel_text = _("Ignore"),
         cancel_callback = function()
-                return
+            return
         end,
         ok_text = _("Disable"),
         ok_callback = function()
-                local Event = require("ui/event")
-                G_reader_settings:delSetting("color_rendering")
-                CanvasContext:setColorRenderingEnabled(false)
-                UIManager:broadcastEvent(Event:new("ColorRenderingUpdate"))
+            local Event = require("ui/event")
+            G_reader_settings:delSetting("color_rendering")
+            CanvasContext:setColorRenderingEnabled(false)
+            UIManager:broadcastEvent(Event:new("ColorRenderingUpdate"))
         end,
     })
 end