Add a *ton* of const and constexpr around the codebase. (#1864)

* Add a *ton* of const and constexpr around the codebase.

This makes the codebase compile without strings being cast to non-const char*. I also went through and added constexpr where appropriate for tons of static data.

* Make process definitions const too

Might as well

src/d/d_meter2.cpp

@@ -3100,7 +3100,7 @@ static leafdraw_method_class l_dMeter2_Method = {
     (process_method_func)dMeter2_Draw,
 };
 
-msg_process_profile_definition g_profile_METER2 = {
+DUSK_PROFILE msg_process_profile_definition DUSK_CONST g_profile_METER2 = {
     /* Layer ID    */ fpcLy_CURRENT_e,
     /* List ID     */ 12,
     /* List Prio   */ fpcPi_CURRENT_e,