Sprite fixes (#2213)

Test still needs more checks that filepaths are valid but I think I got most of the current issues.

Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>

Content.IntegrationTests/Tests/AI/SpriteTest.cs

@@ -0,0 +1,62 @@
+#nullable enable
+using System.Threading.Tasks;
+using NUnit.Framework;
+using Robust.Client.Interfaces.GameObjects.Components;
+using Robust.Client.Interfaces.ResourceManagement;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Interfaces.GameObjects;
+using Robust.Shared.Interfaces.Map;
+using Robust.Shared.Prototypes;
+
+namespace Content.IntegrationTests.Tests.AI
+{
+    [TestFixture]
+    public sealed class SpriteTest : ContentIntegrationTest
+    {
+        /// <summary>
+        ///     Test RSIs and textures are valid
+        /// </summary>
+        [Test]
+        public async Task TestSpritePaths()
+        {
+            var (client, server) = await StartConnectedServerClientPair();
+            await client.WaitIdleAsync();
+            await server.WaitIdleAsync();
+            
+            var resc = client.ResolveDependency<IResourceCache>();
+            var entityManager = client.ResolveDependency<IEntityManager>();
+            var mapManager = client.ResolveDependency<IMapManager>();
+            var prototypeManager = client.ResolveDependency<IPrototypeManager>();
+
+            await client.WaitIdleAsync();
+
+            client.Assert(() =>
+            {
+                var mapId = mapManager.CreateMap();
+                string filePath;
+                var map = mapManager.GetMapEntity(mapId);
+
+                foreach (var proto in prototypeManager.EnumeratePrototypes<EntityPrototype>())
+                {
+                    if (proto.Abstract || !proto.Components.ContainsKey("Sprite"))
+                        continue;
+
+                    var entity = entityManager.SpawnEntity(proto.ID, map.Transform.MapPosition);
+                    var spriteComponent = entity.GetComponent<ISpriteComponent>();
+
+                    foreach (var layer in spriteComponent.AllLayers)
+                    {
+
+                        if (layer.RsiState != null && layer.Rsi != null)
+                        {
+                            filePath = layer.Rsi.Path + "/" + layer.RsiState + ".png";
+                            Assert.That(resc.ContentFileExists(filePath), $"Unable to find {filePath}");
+                        }
+                    }
+                }
+            });
+
+            await client.WaitIdleAsync();
+        }
+    }
+}