CPlayerState: Default CPowerUp constructor

Same behavior but allows the constructor to be considered trivial.

While we're at it, we can make the constructors constexpr, considering
the data structure only holds two primitives.

Runtime/CPlayerState.hpp

@@ -93,8 +93,8 @@ private:
   struct CPowerUp {
     u32 x0_amount = 0;
     u32 x4_capacity = 0;
-    CPowerUp() {}
-    CPowerUp(u32 amount, u32 capacity) : x0_amount(amount), x4_capacity(capacity) {}
+    constexpr CPowerUp() = default;
+    constexpr CPowerUp(u32 amount, u32 capacity) : x0_amount(amount), x4_capacity(capacity) {}
   };
   union {
     struct {