Add support for device buffer address extension

[Jasper-Bekkers]

This is going to be a pretty big/interesting ask, but I'll ask it anyway. Now that VK_EXT_buffer_device_address is out and expected to have wide support in drivers, I'd love for some HLSL extensions to be able to use this in Vulkan.

Or alternatively, and I've had discussions about this with several within Microsoft as well, actual pointer support in HLSL or at least something to the effect of buffer_device_address capabilities.

[simondeschenes]

Being able to use buffer references would be really useful for some of our more complex algorithms.

[Jasper-Bekkers]

#4069 may offer some solace for people landing on this issue.