fix: PlayerSpawnObjectVisibilityTests test instability [Up-Port] (#3548)

This PR addresses some v2.x test instabilities that includes:

- An up-port of #3547.
- A fix for the `InterpolationStopAndStartMotionTest` instabilities.
- A fix for the `BuildTests.BasicBuildTest` instabilities.

[MTT-12645](https://jira.unity3d.com/browse/MTT-12645)

## Changelog

NA

## Testing and Documentation

- Includes integration test modifications.
- No documentation changes or additions were necessary.

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## Backport

This is an up-port of #3547.

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Author: NoelStephensUnity

com.unity.netcode.gameobjects/Tests/Editor/Build/BuildTests.cs

@@ -12,6 +12,8 @@ internal class BuildTests
     {
         public const string DefaultBuildScenePath = "Tests/Editor/Build/BuildTestScene.unity";
 
+        // Increased the Build test timeout from 3 to 10 minutes.
+        [Timeout(900000)]
         [Test]
         public void BasicBuildTest()
         {

com.unity.netcode.gameobjects/Tests/Runtime/NetworkObject/PlayerSpawnObjectVisibilityTests.cs

@@ -63,6 +63,25 @@ protected override void OnCreatePlayerPrefab()
             base.OnCreatePlayerPrefab();
         }
 
+        /// <summary>
+        /// Bypassing this on v1.x as the deferred show message could be processed on the next
+        /// frame from when the client registers having connected.
+        /// </summary>
+        protected override bool ShouldWaitForNewClientToConnect(NetworkManager networkManager)
+        {
+            return false;
+        }
+
+        /// <summary>
+        /// Validate that the player object is spawned on the client side.
+        /// </summary>
+        /// <returns></returns>
+        private bool ClientSpawnedPlayer()
+        {
+            var playerObject = m_ClientNetworkManagers[0].LocalClient.PlayerObject;
+            return playerObject != null && playerObject.IsSpawned && playerObject.IsOwner;
+        }
+
         /// <summary>
         /// Tests the scenario where under a client-server network topology if a player prefab
         /// is spawned by the server with no observers but the player prefab itself has server
@@ -81,7 +100,17 @@ public IEnumerator NetworkShowOnSpawnTest([Values] PlayerSpawnStages spawnStage)
 
             yield return CreateAndStartNewClient();
 
-            yield return new WaitForSeconds(0.25f);
+            // Wait for the new client to connect
+            yield return WaitForClientsConnectedOrTimeOut();
+            AssertOnTimeout($"Timed out waiting for client to connect!");
+            OnNewClientStartedAndConnected(m_ClientNetworkManagers[0]);
+
+            // Wait for the new client to have spawned the player
+            yield return WaitForConditionOrTimeOut(ClientSpawnedPlayer);
+            AssertOnTimeout($"Timed out waiting for client to spawn its player object!");
+
+            // Provide some time to assure there are no additional attempts to spawn the same instance
+            yield return new WaitForSeconds(0.5f);
 
             NetcodeLogAssert.LogWasNotReceived(LogType.Warning, new Regex("but it is already in the spawned list!"));
             var client = GetNonAuthorityNetworkManager();

com.unity.netcode.gameobjects/Tests/Runtime/NetworkTransform/InterpolationStopAndStartMotionTest.cs

@@ -270,7 +270,8 @@ public override void OnUpdate()
                             // Add it to the table of state updates
                             var stateEntry = new StateEntry()
                             {
-                                TimeAdded = Time.realtimeSinceStartup,
+                                // Use the server time to get the valid "relative" time since the session started.
+                                TimeAdded = NetworkManager.ServerTime.TimeAsFloat,
                                 State = m_PosInterpolator.InterpolateState,
                             };