Recommit "[LV] Move runtime pointer size check to LVP::plan()."

Re-apply 25fbe803, with a small update to emit the right remark
class.

Original message:
    [LV] Move runtime pointer size check to LVP::plan().

    This removes the need for the remaining doesNotMeet check and instead
    directly checks if there are too many runtime checks for vectorization
    in the planner.

    A subsequent patch will adjust the logic used to decide whether to
    vectorize with runtime to consider their cost more accurately.

    Reviewed By: lebedev.ri