Convert IDGenerator uint32 -> size_t

Signed-off-by: Chris Burel <burelc@amazon.com>

Gems/EMotionFX/Code/MCore/Source/IDGenerator.cpp

@@ -15,8 +15,8 @@ namespace MCore
 {
     // constructor
     IDGenerator::IDGenerator()
+        : mNextID{0}
     {
-        mNextID.SetValue(0);
     }
 
 
@@ -27,10 +27,10 @@ namespace MCore
 
 
     // get a unique id
-    uint32 IDGenerator::GenerateID()
+    size_t IDGenerator::GenerateID()
     {
-        const uint32 result = mNextID.Increment();
-        MCORE_ASSERT(result != MCORE_INVALIDINDEX32); // reached the limit
+        const size_t result = mNextID++;
+        MCORE_ASSERT(result != InvalidIndex); // reached the limit
         return result;
     }
 } // namespace MCore

Gems/EMotionFX/Code/MCore/Source/IDGenerator.h

@@ -28,10 +28,10 @@ namespace MCore
          * This is thread safe.
          * @return The unique id.
          */
-        uint32 GenerateID();
+        size_t GenerateID();
 
     private:
-        AtomicUInt32    mNextID;    /**< The id used for the next GenerateID() call. */
+        AZStd::atomic<size_t>    mNextID;    /**< The id used for the next GenerateID() call. */
 
         /**
          * Default constructor.