Revert "[CaptureTracking] Ignore ephemeral values when determining po… (#71066)

Unfortunately the commit (D123162) introduced a mis-compile
(https://github.com/llvm/llvm-project/issues/70547), which wasn't fixed
by the alternative fix (c0de28b9)

I think as long as the call considered as ephemeral is not removed, we
need to be conservative. To address the correctness issue quickly, I
think we should revert the patch (as this patch does, it doens't revert
cleanly)

This reverts commit 17fdaccc.

Fixes https://github.com/llvm/llvm-project/issues/70547