Fix ios gpu crash + misc cleanup (#1603)

Gems/Atom/RHI/Metal/Code/Source/RHI/ArgumentBuffer.cpp

@@ -334,9 +334,8 @@ namespace AZ
             if(m_argumentBuffer.IsValid())
             {
                 m_device->GetArgumentBufferAllocator().DeAllocate(m_argumentBuffer);
-            }
-#endif
-            
+            }            
+#else
             if(m_argumentBuffer.IsValid())
             {
                 m_device->QueueForRelease(m_argumentBuffer);
@@ -346,7 +345,11 @@ namespace AZ
             {
                 m_device->QueueForRelease(m_constantBuffer);
             }
+#endif
 
+            m_argumentBuffer = {};
+            m_constantBuffer = {};
+            
             [m_argumentEncoder release];
             m_argumentEncoder = nil;
              

Gems/Atom/RHI/Metal/Code/Source/RHI/CommandListBase.cpp

@@ -78,8 +78,9 @@ namespace AZ
                     id<MTLRenderCommandEncoder> renderEncoder = GetEncoder<id<MTLRenderCommandEncoder>>();
                     for (id<MTLHeap> residentHeap : *m_residentHeaps)
                     {
+                        //MTLRenderStageVertex is not added to this as it was causing an immediate gpu crash on ios (first buffer commit)
                         [renderEncoder useHeap : residentHeap
-                                       stages  : MTLRenderStageVertex | MTLRenderStageFragment];
+                                       stages  : MTLRenderStageFragment];
                     }
                     break;
                 }

Gems/Atom/RHI/Metal/Code/Source/RHI/ShaderResourceGroupPool.cpp

@@ -55,7 +55,6 @@ namespace AZ
             ShaderResourceGroup& group = static_cast<ShaderResourceGroup&>(resourceBase);
             for (size_t i = 0; i < RHI::Limits::Device::FrameCountMax; ++i)
             {
-                group.m_compiledArgBuffers[i]->Shutdown();
                 group.m_compiledArgBuffers[i] = nullptr;
             }
             Base::ShutdownResourceInternal(resourceBase);