If using Vulkan backend and either vertex_size or index_size is not aligned to VkPhysicalDeviceLimits::nonCoherentAtomSize, then the call to vkFlushMappedMemoryRanges in ImGui_ImplVulkan_RenderDrawData will result to validation error.
- It adds an optional feature to support dynamic linkage of Vulkan instead of using default linkage.
- It is now possible to have several potentially working implementation and whenever the Vulkan library was available it can work.
This allows for binding the pipeline/sending draw commands
(via `ImGui_ImplVulkan_RenderDrawData`) against any subpass, rather than
being restricted to only the first subpass.
Without this, attempting to bind the pipeline against a subpass other than
the first one results in validation layer errors and, at worst, some drivers
failing if the subpass attachments differ.
