Change the implemented interface of the Elasticsuite Search Engine.

[romainruaud]

This one is a pre-requisite for fixing #855

This is just changing the implemented interface from \Magento\Framework\Api\Search\SearchInterface to \Magento\Search\Api\SearchInterface.

The \Magento\Search\Api\SearchInterface is an @api flagged one also, and is empty and just inheriting the \Magento\Framework\Api\Search\SearchInterface : https://github.com/magento/magento2/blob/2.2-develop/app/code/Magento/Search/Api/SearchInterface.php

So for me, this is not too much risky to inherit this interface instead of the previous one, since they are the same for now. Also, the new interface is part of the Magento_Search module but we already depend on it.

Regards

[romainruaud]

It's also more logical to implement this interface since this is the one we declared on our config here : https://github.com/Smile-SA/elasticsuite/blob/master/src/module-elasticsuite-core/etc/di.xml#L65