[SLP] NFC. Replace TreeEntry::setOperandsInOrder with VLOperands. (#118949)
To reduce repeated code, TreeEntry::setOperandsInOrder will be replaced
by VLOperands.
Arg_size will be provided to make sure other operands will not be
reorderd when VL[0] is IntrinsicInst (because APO is a boolean value).
In addition, BoUpSLP::reorderInputsAccordingToOpcode will also be
removed since it is simple.