fix a lot of low level cppcheck warnings (#9623)

* simplify the observer pattern, since all the called functions are const getters.
* use arduino macro over std: for numerical values and refactor local variables in drawScrollbar()
* oh, so Cppcheck actually complained about const pointers not being const.
* slowly getting out of ifdef hell
* fix inkHUD warnings as well
* last 2 check warnings
* git checks should fail on low defects from now on

src/graphics/niche/InkHUD/WindowManager.cpp

@@ -396,7 +396,7 @@ void InkHUD::WindowManager::autoshow()
 {
     // Don't perform autoshow if a system applet has exclusive use of the display right now
     // Note: lockRequests prevents autoshow attempting to hide menuApplet
-    for (SystemApplet *sa : inkhud->systemApplets) {
+    for (const SystemApplet *sa : inkhud->systemApplets) {
         if (sa->lockRendering || sa->lockRequests)
             return;
     }