[SLP]Add final resize to ShuffleCostEstimator::finalize member function and...

[SLP]Add final resize to ShuffleCostEstimator::finalize member function and basic add member functions.

Implemented the reshuffling in finalize member function + add basic
support for add member functions, used during vector build.

Part of D110978

Differential Revision: https://reviews.llvm.org/D148279