Vulkan: Restore CommandBuffer to namespace vk

Moved vk::CommandBuffer and vk::SecondaryCommandBuffer to vk::priv:: and
aliased vk::CommandBuffer to one or the other.  This allows the rest of
the classes to continue seeing vk::CommandBuffer as they used to do.
Used a special alias for the primary command buffer that gets submitted
(vk::PrimaryCommandBuffer).

Bug: angleproject:3136
Change-Id: I61236fd182230991db7395d05e3da3be5e3f45be
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1534456
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/RenderbufferVk.cpp b/src/libANGLE/renderer/vulkan/RenderbufferVk.cpp
index a77d986..1e485a9 100644
--- a/src/libANGLE/renderer/vulkan/RenderbufferVk.cpp
+++ b/src/libANGLE/renderer/vulkan/RenderbufferVk.cpp
@@ -93,7 +93,7 @@
                                         &mImageView, 0, 1));
 
         // TODO(jmadill): Fold this into the RenderPass load/store ops. http://anglebug.com/2361
-        CommandBufferT *commandBuffer = nullptr;
+        vk::CommandBuffer *commandBuffer = nullptr;
         ANGLE_TRY(mImage->recordCommands(contextVk, &commandBuffer));
 
         if (isDepthOrStencilFormat)
@@ -143,7 +143,7 @@
     uint32_t rendererQueueFamilyIndex = contextVk->getRenderer()->getQueueFamilyIndex();
     if (mImage->isQueueChangeNeccesary(rendererQueueFamilyIndex))
     {
-        CommandBufferT *commandBuffer = nullptr;
+        vk::CommandBuffer *commandBuffer = nullptr;
         ANGLE_TRY(mImage->recordCommands(contextVk, &commandBuffer));
         mImage->changeLayoutAndQueue(aspect, vk::ImageLayout::ColorAttachment,
                                      rendererQueueFamilyIndex, commandBuffer);