renderer_base: Add prepare/cleanup function interface

This should be called by the video dumper backend to tell the video core to create necessary buffers/storage, etc.

src/video_core/renderer_base.h

@@ -13,6 +13,10 @@ namespace Frontend {
 class EmuWindow;
 }
 
+namespace FrameDumper {
+class Backend;
+}
+
 class RendererBase : NonCopyable {
 public:
     /// Used to reference a framebuffer
@@ -30,6 +34,12 @@ public:
     /// Shutdown the renderer
     virtual void ShutDown() = 0;
 
+    /// Prepares for video dumping (e.g. create necessary buffers, etc)
+    virtual void PrepareVideoDumping() = 0;
+
+    /// Cleans up after video dumping is ended
+    virtual void CleanupVideoDumping() = 0;
+
     /// Updates the framebuffer layout of the contained render window handle.
     void UpdateCurrentFramebufferLayout();