Improve Buffer Textures and flush Image Stores (#2088)

* Improve Buffer Textures and flush Image Stores

Fixes a number of issues with buffer textures:

- Reworked Buffer Textures to create their buffers in the TextureManager, then bind them with the BufferManager later.
  - Fixes an issue where a buffer texture's buffer could be invalidated after it is bound, but before use.
- Fixed width unpacking for large buffer textures. The width is now 32-bit rather than 16.
- Force buffer textures to be rebound whenever any buffer is created, as using the handle id wasn't reliable, and the cost of binding isn't too high.

Fixes vertex explosions and flickering animations in UE4 games.

* Set ImageStore flag... for ImageStore.

* Check the offset and size.

Ryujinx.Graphics.Gpu/Image/TexturePool.cs

@@ -172,8 +172,6 @@ namespace Ryujinx.Graphics.Gpu.Image
         /// <returns>The texture information</returns>
         private TextureInfo GetInfo(TextureDescriptor descriptor, out int layerSize)
         {
-            int width         = descriptor.UnpackWidth();
-            int height        = descriptor.UnpackHeight();
             int depthOrLayers = descriptor.UnpackDepth();
             int levels        = descriptor.UnpackLevels();
 
@@ -190,6 +188,9 @@ namespace Ryujinx.Graphics.Gpu.Image
 
             Target target = descriptor.UnpackTextureTarget().Convert((samplesInX | samplesInY) != 1);
 
+            int width = target == Target.TextureBuffer ? descriptor.UnpackBufferTextureWidth() : descriptor.UnpackWidth();
+            int height = descriptor.UnpackHeight();
+
             // We use 2D targets for 1D textures as that makes texture cache
             // management easier. We don't know the target for render target
             // and copies, so those would normally use 2D targets, which are