chore: Improve performance of NetworkList set operation (#3587)

continues: #3585 

This PR adds an equality check to the `NetworkList<T>` indexer setter,
aligning its behavior with `NetworkVariable<T>.Value`. Since
`NetworkList<T>` already constrains `T` to `IEquatable<T>`, this change
is both safe and broadly applicable. It avoids redundant assignments
when the new value is equal to the current value, which improves runtime
efficiency and avoids unnecessary event dispatch and network
synchronization.

## Changelog

- Changed: Optimized `NetworkList<T>` indexer setter to skip operations
when the new value equals the existing value, improving performance by
avoiding unnecessary list events and network synchronization.

## Testing & QA

This is a very small optimization in an area of code that is deeply
covered by unit and integration tests. No manual testing is required.

## Documentation

As there are no API or behaviour changes, no documentation is required

## Backport

This is a new optimization and so doesn't need to be backported

---------

Co-authored-by: Yuto Harada <[email protected]>

Author: EmandM

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -19,6 +19,8 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Changed
 
+- Optimized `NetworkList<T>` indexer setter to skip operations when the new value equals the existing value, improving performance by avoiding unnecessary list events and network synchronization. (#3587)
+
 
 ## [2.5.0] - 2025-08-01
 

com.unity.netcode.gameobjects/Runtime/NetworkVariable/Collections/NetworkList.cs

@@ -617,6 +617,13 @@ public T this[int index]
                 }
 
                 var previousValue = m_List[index];
+
+                // Only trigger an event if the value has changed
+                if (NetworkVariableSerialization<T>.AreEqual(ref previousValue, ref value))
+                {
+                    return;
+                }
+
                 m_List[index] = value;
 
                 var listEvent = new NetworkListEvent<T>()