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/mesh/api/PacketAPI.h

@@ -17,7 +17,7 @@ class PacketAPI : public PhoneAPI, public concurrency::OSThread
     virtual int32_t runOnce();
 
   protected:
-    PacketAPI(PacketServer *_server);
+    explicit PacketAPI(PacketServer *_server);
     // Check the current underlying physical queue to see if the client is fetching packets
     bool checkIsConnected() override;