layers: Refactor CmdBlitImage for PreCalls
layers: Refactor CmdBlitImage for PreCalls

Moved validation and state updates into separate helper functions.

Change-Id: I8427cd2c35e85f28edfb589a9dc08220eb5fa817

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools