No product found when using "Show all" on product list

[FlinthDevs]

Using the "Show all" feature on products lists returns no result.

Preconditions

Magento Version : 2.3.1 CE
ElasticSuite Version : 2.8.0
Environment : Developper

Steps to reproduce

1. Enable "Allow all products per page" option in admin
2. Go on a product list page (category view or fulltext search)
3. Select "All" in "Show X per page" select

Expected result

1. All products are listed

Actual result

1. No products are found and the message "We can't find products matching the selection." displayed.

[rbayet]

Partially fixed by #1431 (which re-introduces \Smile\ElasticsuiteCatalog\Model\ResourceModel\Product\Fulltext\Collection::loadProductCounts), but also requires to fix this in \Smile\ElasticsuiteCatalog\Model\ResourceModel\Product\Fulltext\Collection::prepareRequest ?

        // Pagination params.
        $size = $this->_pageSize ? $this->_pageSize : 0;

(It was historically

        // Pagination params.
        $size = $this->_pageSize ? $this->_pageSize : $this->getSize();
```)

[rbayet]

See also #1428

[romainruaud]

Fixed by associated PR #1460