Initial support for GPU channels (#2372)

* Ground work for separate GPU channels

* Rename TextureManager to TextureCache

* Decouple texture bindings management from the texture cache

* Rename BufferManager to BufferCache

* Decouple buffer bindings management from the buffer cache

* More comments and proper disposal

* PR feedback

* Force host state update on channel switch

* Typo

* PR feedback

* Missing using

Ryujinx.Graphics.Gpu/Image/TexturePoolCache.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 
 namespace Ryujinx.Graphics.Gpu.Image
@@ -7,7 +8,7 @@ namespace Ryujinx.Graphics.Gpu.Image
     /// This can keep multiple texture pools, and return the current one as needed.
     /// It is useful for applications that uses multiple texture pools.
     /// </summary>
-    class TexturePoolCache
+    class TexturePoolCache : IDisposable
     {
         private const int MaxCapacity = 4;
 
@@ -72,5 +73,19 @@ namespace Ryujinx.Graphics.Gpu.Image
 
             return pool;
         }
+
+        /// <summary>
+        /// Disposes the texture pool cache.
+        /// It's an error to use the texture pool cache after disposal.
+        /// </summary>
+        public void Dispose()
+        {
+            foreach (TexturePool pool in _pools)
+            {
+                pool.Dispose();
+            }
+
+            _pools.Clear();
+        }
     }
 }