Implemented vkCmdBeginRenderPass and vkCmdEndRenderPass.
The RenderPass object begin and end are noop for now, but
the framebuffer gets cleared within vkCmdBeginRenderPass.

Bug b/119620965 b/118619338

Change-Id: I8e1f2932d9d52b3dcb5c10d4e60cba83b28bb95d
Reviewed-on: https://swiftshader-review.googlesource.com/c/23108Reviewed-by: Corentin Wallez <cwallez@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>