Option to initialize undefined/discarded data with pattern

This feature has been available in Renderdoc since version 1.9 (see [Release Notes](https://github.com/baldurk/renderdoc/releases/tag/v1.9))

When an image is not initialized, transitioned from UNDEFINED, or used as an attachment with *_DONT_CARE, it fills the image with a recognizable pattern. Buffers are initialized with `0xD15CAD3D`.

This feature is excellent, but Renderdoc is not always capable of capturing workloads that use new or rare Vulkan features.

I would like to have a similar option in ValidationLayers. It would visually indicate that your workload is relying on undefined behavior, which may not be visible on one hardware vendor but could appear when using another.

Additionally, an option to use different values like `0x00`, `0xFF`, or `0xCC` for uninitialized memory would be useful as well.

The issue does not name implementation files, tests, or an entry point. Start by locating how Vulkan ValidationLayers handles undefined, discarded, and DONT_CARE image or buffer data, then define the configuration and validation coverage needed for recognizable patterns and alternate fill values.

Written by the indexing model from the issue text.