[clang] [CIR] Upstream CastOp and scalar conversions (PR #130690)

[Andy Kaylor via cfe-commits]

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+// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o %t.cir
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andykaylor wrote:

Can you expand this test to cover all the cast types you're adding (or remove any that can't be supported yet)?

https://github.com/llvm/llvm-project/pull/130690