Cross-vendor version of VK_NV_shader_image_footprint

This issue is similar to #1423
VK_NV_shader_image_footprint to my understanding is a DirectX 12 Ultimate version of sampler feedback, is there anything to be said about a possible VK_EXT_shader_image_footprint or VK_EXT_sampler_feedback (so novices will quickly know what this extension does)? Right now the only possible way to use a "Sampler feedback" is either use DX 12.1 or have an Nvidia card.

Start by reading issue #1423 and the description of VK_NV_shader_image_footprint, then compare the stated DirectX 12 sampler-feedback capability with the requested cross-vendor Vulkan scope. A useful outcome would be a decided extension direction and a clear explanation of what novice users should understand, rather than an implementation patch.

Written by the indexing model from the issue text.