[SLP]Allow to reorder nodes with >2 scalar values.

tryToVectorizeList function allows to reorder only 2 scalars. Patch
allows to reorder >2 scalars. Also, to avoid possible regressions, it
allows extra vectorization of the remaining parts of the scalars
elements if possible.

Part of D57059.

Differential Revision: https://reviews.llvm.org/D103247