[llvm] [X86][AArch64][SPIRV] add more tests for `ldexp`/`frexp` (PR #208462)

[Folkert de Vries via llvm-commits]

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folkertdev wrote:

This actually promotes and uses the libcall now. I think that is better?  Certainly in terms of code size.

https://github.com/llvm/llvm-project/pull/208462