Reapply [IR] Avoid creating icmp/fcmp constant expressions (#92885)

Reapply after https://github.com/llvm/llvm-project/pull/93548,
which should address the lldb failure on macos.

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Do not create icmp/fcmp constant expressions in IRBuilder etc anymore,
i.e. treat them as "undesirable". This is in preparation for removing
them entirely.

Part of:
https://discourse.llvm.org/t/rfc-remove-most-constant-expressions/63179