[clang] Add concepts for raw buffers (PR #119643)

[Justin Bogner via cfe-commits]

bogner wrote:

This should really be talking about concepts for structured buffers, not raw buffers. At the HLSL language level, there is nothing called a RawBuffer - there is ByteAddressBuffer and various kinds of StructuredBuffer, which are represented lower in the stack as a "raw" buffer. Given that there are no concepts for ByteAddressBuffer (since it isn't a template), these concepts apply specifically to structured buffers, so the naming should reflect that.

https://github.com/llvm/llvm-project/pull/119643