[IVDescriptors] Bail out instead of asserting that order is expected.

When dealing with multiple phis that depend on each other, the order
might have been changed and may not match the expectation. If that
happens, bail out, rather than asserting.

Fixes https://github.com/llvm/llvm-project/issues/54218
Fixes https://github.com/llvm/llvm-project/issues/54233
Fixes https://github.com/llvm/llvm-project/issues/54254