[PATCH 1/2] vinyl: refactor vy_mem_iterator_seek

[Vladimir Davydov]

On Thu, Feb 28, 2019 at 12:37:19AM +0300, Vladimir Davydov wrote:
>  - Don't pass iterator_type to vy_mem_iterator_seek and functions called
>    by it. Instead pass only a key and jump to the first statement
>    following the key according to the iterator search criteria. Turns
>    out this is enough for memory iterator implementation.
>  - Fold EQ check in vy_mem_iterator_seek to avoid code duplication.
>  - Drop vy_mem_iterator_start and use vy_mem_iterator_seek directly.
> ---
> https://github.com/tarantool/tarantool/commits/dv/vy-optimize-next-key

Pushed to 2.1. Will backport to 1.10 once stability test passes.