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

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skc7 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?

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