MemoryPatches: In-class initialize is_enabled state for MemoryPatch instances

Given this is what occurs in both constructors (as one just passes
through to another), we can just initialize the member directly.

While we're at it, amend the struct to follow the general ordering
convention of:

<new types>
<functions>
<variables>

Source/Core/Common/Debug/MemoryPatches.h

@@ -20,12 +20,12 @@ struct MemoryPatch
     Disabled
   };
 
-  u32 address;
-  std::vector<u8> value;
-  State is_enabled;
-
   MemoryPatch(u32 address, std::vector<u8> value);
   MemoryPatch(u32 address, u32 value);
+
+  u32 address;
+  std::vector<u8> value;
+  State is_enabled = State::Enabled;
 };
 
 class MemoryPatches