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/gps/RTC.cpp

@@ -312,7 +312,7 @@ const char *RtcName(RTCQuality quality)
  * @param t The time to potentially set the RTC to.
  * @return True if the RTC was set to the provided time, false otherwise.
  */
-RTCSetResult perhapsSetRTC(RTCQuality q, struct tm &t)
+RTCSetResult perhapsSetRTC(RTCQuality q, const struct tm &t)
 {
     /* Convert to unix time
     The Unix epoch (or Unix time or POSIX time or Unix timestamp) is the number of seconds that have elapsed since January 1, 1970

src/gps/RTC.h

@@ -41,7 +41,7 @@ extern uint32_t lastSetFromPhoneNtpOrGps;
 
 /// If we haven't yet set our RTC this boot, set it from a GPS derived time
 RTCSetResult perhapsSetRTC(RTCQuality q, const struct timeval *tv, bool forceUpdate = false);
-RTCSetResult perhapsSetRTC(RTCQuality q, struct tm &t);
+RTCSetResult perhapsSetRTC(RTCQuality q, const struct tm &t);
 
 /// Return a string name for the quality
 const char *RtcName(RTCQuality quality);