[X86] Add baseline test for X86 conditional load/store optimization bug (#163354)

This PR adds a baseline test that exposes a bug in the current
`combineX86CloadCstore` optimization. The generated assembly
demonstrates incorrect behavior when the optimization is applied without
proper constraints.

Without any assumptions about `X` this transformation is only valid when
`Y` is a non zero power of two/single-bit mask.
```cpp
      // res, flags2 = sub 0, (and (xor X, -1), Y)
      // cload/cstore ..., cond_ne, flag2
      // ->
      // res, flags2 = sub 0, (and X, Y)
      // cload/cstore ..., cond_e, flag2
```

In the provided test case, the value in `%al` is unknown at compile
time. If `%al` contains `0`, the optimization cannot be applied, because
`(and (xor X, -1), 0)` is not equal to `(and X, 0)`.

Fix: https://github.com/llvm/llvm-project/pull/163353

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