feat: Add NetworkList getter and redo NetworkList tests (#3690)

## Purpose of this PR

Add setter onto `NetworkList` that allows an update to be "forced" even
if the value was not changed.

fixes: #3657 

### Jira ticket
MTT-13366

### Changelog

- Added: A `Set` function onto the `NetworkList` that takes an optional
parameter that will force the update to be processed and will ignore the
equality check.

## Documentation

- No documentation changes or additions were necessary.

## Testing & QA (How your changes can be verified during release
Playtest)

### Functional Testing

- [ ] `Manual testing done`

_Automated tests:_
- [x] `Covered by existing automated tests`
- [x] `Covered by new automated tests`

_Does the change require QA team to:_

- [ ] `Review automated tests`?
- [ ] `Execute manual tests`?
- [ ] `Provide feedback about the PR`?

If any boxes above are checked the QA team will be automatically added
as a PR reviewer.

## Backports

This is a 2.x only change

---------

Co-authored-by: Noel Stephens <[email protected]>

Author: EmandM

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -11,6 +11,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 ### Added
 
 - Clicking on the Help icon in the inspector will now redirect to the relevant documentation. (#3663)
+- Added a `Set` function onto `NetworkList` that takes an optional parameter that forces an update to be processed even if the current value is equal to the previous value. (#3690)
 
 ### Changed
 

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

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 using Unity.Collections;
 
 namespace Unity.Netcode
@@ -597,45 +598,60 @@ public void RemoveAt(int index)
         }
 
         /// <summary>
-        /// Gets or sets the element at the specified index in the <see cref="NetworkList{T}"/>.
+        /// Sets the element at the specified index in the <see cref="NetworkList{T}"/>.
         /// </summary>
         /// <remarks>
-        /// This method checks for write permissions before setting the value.
+        /// This method checks for write permissions and equality before setting and updating the value.
         /// </remarks>
-        /// <param name="index">The zero-based index of the element to get or set.</param>
-        /// <value>The element at the specified index.</value>
-        public T this[int index]
+        /// <param name="index">The zero-based index of the element to set.</param>
+        /// <param name="value">The new value to set at the given index</param>
+        /// <param name="forceUpdate">
+        /// Ignores the equality check when setting the value.
+        /// This option can send unnecessary updates to all clients when the value hasn't changed.
+        /// </param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Set(int index, T value, bool forceUpdate = false)
         {
-            get => m_List[index];
-            set
+            // check write permissions
+            if (CannotWrite)
             {
-                // check write permissions
-                if (CannotWrite)
-                {
-                    LogWritePermissionError();
-                    return;
-                }
+                LogWritePermissionError();
+                return;
+            }
 
-                var previousValue = m_List[index];
+            var previousValue = m_List[index];
 
-                // Only trigger an event if the value has changed
-                if (NetworkVariableSerialization<T>.AreEqual(ref previousValue, ref value))
-                {
-                    return;
-                }
+            // Only trigger an event if the value has changed
+            if (!forceUpdate && NetworkVariableSerialization<T>.AreEqual(ref previousValue, ref value))
+            {
+                return;
+            }
 
-                m_List[index] = value;
+            m_List[index] = value;
 
-                var listEvent = new NetworkListEvent<T>()
-                {
-                    Type = NetworkListEvent<T>.EventType.Value,
-                    Index = index,
-                    Value = value,
-                    PreviousValue = previousValue
-                };
+            var listEvent = new NetworkListEvent<T>()
+            {
+                Type = NetworkListEvent<T>.EventType.Value,
+                Index = index,
+                Value = value,
+                PreviousValue = previousValue
+            };
 
-                HandleAddListEvent(listEvent);
-            }
+            HandleAddListEvent(listEvent);
+        }
+
+        /// <summary>
+        /// Gets or sets the element at the specified index in the <see cref="NetworkList{T}"/>.
+        /// </summary>
+        /// <remarks>
+        /// This method checks for write permissions before setting the value.
+        /// </remarks>
+        /// <param name="index">The zero-based index of the element to get or set.</param>
+        /// <value>The element at the specified index.</value>
+        public T this[int index]
+        {
+            get => m_List[index];
+            set => Set(index, value);
         }
 
         /// <summary>