[LV] Perform recurrence sinking directly on VPlan.

This patch updates LV to sink recipes directly using the VPlan use
chains. The initial patch only moves sinking to be purely VPlan-based.
Follow-up patches will move legality checks to VPlan as well.

At the moment, there's a single test failure remaining.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D142589