[LegalizeTypes] Pre-size the SmallVectors in ScalarizeVecRes_StrictFPOp and...

[LegalizeTypes] Pre-size the SmallVectors in ScalarizeVecRes_StrictFPOp and SplitVecRes_StrictFPOp so we don't have to call push_back. NFCI

This avoids grow checking/handling in each iteration of the loop.