[X86] Add tests showing failure to concat fma chain which share concatenated operands (#173403)

We often have fma chains that reuse operands down the chain (e.g mathlib
taylor series expansion) - FMA(FMA(X,Y,Z),X,W) etc.

For these cases combineConcatVectorOps fails to account that the same
operands will be concatenated down the recursion chain.

GitOrigin-RevId: 4e44e8761795d4672121368929b9c99f6dbaffa7