[X86] Fold xor(truncate(xor(x,c1)),c2) -> xor(truncate(x),xor(truncate(c1),c2))

Fixes PR47603

This should probably be transferable to DAGCombine - the main limitation with the existing trunc(logicop) DAG fold is we don't know if legalization has tried to promote truncated logicops already. We might be able to peek through extensions as well.