[dxvk] Add DXVK context method to transparently flush the command list

This is identical to what the D3D11 function did, but having it in this
place will allow us to potentially implement better flush heuristics
based on work done on the CS thread.

src/d3d11/d3d11_context_imm.cpp

@@ -101,13 +101,8 @@ namespace dxvk {
     if (m_csIsBusy || m_csChunk->commandCount() != 0) {
       // Add commands to flush the threaded
       // context, then flush the command list
-      EmitCs([dev = m_device] (DxvkContext* ctx) {
+      EmitCs([] (DxvkContext* ctx) {
-        dev->submitCommandList(
+        ctx->flushCommandList();
-          ctx->endRecording(),
-          nullptr, nullptr);
-        
-        ctx->beginRecording(
-          dev->createCommandList());
       });
       
       FlushCsChunk();

src/dxvk/dxvk_context.cpp

@@ -63,6 +63,16 @@ namespace dxvk {
     m_cmd->endRecording();
     return std::exchange(m_cmd, nullptr);
   }
+
+
+  void DxvkContext::flushCommandList() {
+    m_device->submitCommandList(
+      this->endRecording(),
+      nullptr, nullptr);
+    
+    this->beginRecording(
+      m_device->createCommandList());
+  }
   
   
   void DxvkContext::beginQuery(const DxvkQueryRevision& query) {

src/dxvk/dxvk_context.h

@@ -62,6 +62,14 @@ namespace dxvk {
      * \returns Active command list
      */
     Rc<DxvkCommandList> endRecording();
+
+    /**
+     * \brief Flushes command buffer
+     * 
+     * Transparently submits the current command
+     * buffer and allocates a new one.
+     */
+    void flushCommandList();
     
     /**
      * \brief Begins generating query data