Use mag_power to make callsites more concise

src/systems/si/include/units/isq/si/catalytic_activity.h

@@ -58,8 +58,7 @@ struct exakatal : prefixed_unit<exakatal, exa, katal> {};
 struct zettakatal : prefixed_unit<zettakatal, zetta, katal> {};
 struct yottakatal : prefixed_unit<yottakatal, yotta, katal> {};
 
-struct enzyme_unit :
-    named_scaled_unit<enzyme_unit, "U", as_magnitude<ratio(1, 60)>() * pow<-6>(as_magnitude<10>()), katal> {};
+struct enzyme_unit : named_scaled_unit<enzyme_unit, "U", as_magnitude<ratio(1, 60)>() * mag_power<10, -6>(), katal> {};
 
 struct dim_catalytic_activity :
     isq::dim_catalytic_activity<dim_catalytic_activity, katal, dim_time, dim_amount_of_substance> {};

src/systems/si/include/units/isq/si/energy.h

@@ -56,8 +56,8 @@ struct yottajoule : prefixed_unit<yottajoule, yotta, joule> {};
 // N.B. electron charge (and eV) is an exact constant:
 // https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf#page=147
 struct electronvolt :
-    named_scaled_unit<electronvolt, "eV",
-                      as_magnitude<ratio(1'602'176'634, 1'000'000'000)>() * pow<-19>(as_magnitude<10>()), joule> {};
+    named_scaled_unit<electronvolt, "eV", as_magnitude<ratio(1'602'176'634, 1'000'000'000)>() * mag_power<10, -19>(),
+                      joule> {};
 struct gigaelectronvolt : prefixed_unit<gigaelectronvolt, giga, electronvolt> {};
 
 struct dim_energy : isq::dim_energy<dim_energy, joule, dim_force, dim_length> {};

src/systems/si/include/units/isq/si/mass.h

@@ -80,8 +80,8 @@ struct yottatonne : prefixed_unit<yottatonne, yotta, tonne> {};
 
 struct dalton :
     named_scaled_unit<dalton, "Da",
-                      as_magnitude<ratio(16'605'390'666'050, 10'000'000'000'000)>() * pow<-27>(as_magnitude<10>()),
-                      kilogram> {};
+                      as_magnitude<ratio(16'605'390'666'050, 10'000'000'000'000)>() * mag_power<10, -27>(), kilogram> {
+};
 
 struct dim_mass : isq::dim_mass<kilogram> {};