[clang] [CIR][AMDGPU] Adds lowering for amdgcn extended image sample/gather4 builtins (PR #201761)

[Rana Pratap Reddy via cfe-commits]

ranapratap55 wrote:

> [clang/test/CodeGen/builtins-extended-image.c](https://github.com/llvm/llvm-project/blob/main/clang/test/CodeGen/builtins-extended-image.c) OGCG has tests covering `v4f16(half)` types which are missing in the tests here. Could you add them in this PR?

updated in latest revision. Thanks.

https://github.com/llvm/llvm-project/pull/201761