refactor: move compare.h and random.h to mp_units.core

src/mp-units-core.cpp

@@ -8,4 +8,8 @@ export
 {
 // core
 #include <mp-units/core.h>
+
+// utility
+#include <mp-units/compare.h>
+#include <mp-units/random.h>
 }

src/mp-units-systems.cpp

@@ -26,7 +26,5 @@ export
 
 // utility
 #include <mp-units/chrono.h>
-#include <mp-units/compare.h>
 #include <mp-units/math.h>
-#include <mp-units/random.h>
 }