Wrong total_count on GET /V1/inventory/export-stock-salable-qty/{salesChannelType}/{salesChannelCode} API

### Preconditions
1. MSI tagged with 1.2.7-beta3, but also previous versions have the same bug;
2. A fixed number of products, in this example 95486.

### Steps to reproduce
Call the `GET /V1/inventory/export-stock-salable-qty/{salesChannelType}/{salesChannelCode}` [API](https://adobe-commerce.redoc.ly/2.4.7-admin/tag/inventoryexport-stock-salable-qtysalesChannelTypesalesChannelCode#operation/GetV1InventoryExportstocksalableqtySalesChannelTypeSalesChannelCode)
```
curl --location --globoff 'https://127.0.0.1:8080/rest/V1/inventory/export-stock-salable-qty/{salesChannelType}/{salesChannelCode}?searchCriteria[currentPage]=5&searchCriteria[pageSize]=1000' \
--header 'Authorization: Bearer TOKEN'
```

### Expected result
`total_count` should return the number of product with stock item in the select sales channel:
```
{
"items": [
{
"sku": "SKU_1",
"qty": 0,
"is_salable": false
},
[...]
{
"sku": "SKU_1000",
"qty": 0,
"is_salable": false
}
],
"search_criteria": {
"filter_groups": [],
"page_size": 1000,
"current_page": 5
},
"total_count": 95486
}
```

### Actual result
`total_count` return instead the number of items in the current response:
```
{
"items": [
{
"sku": "SKU_1",
"qty": 0,
"is_salable": false
},
[...]
{
"sku": "SKU_1000",
"qty": 0,
"is_salable": false
}
],
"search_criteria": {
"filter_groups": [],
"page_size": 1000,
"current_page": 5
},
"total_count": 1000
}
```

You can crearly see the bug [here](https://github.com/magento/inventory/blob/1.2.7-beta3/InventoryExportStock/Model/ExportStockSalableQtyBySalesChannel.php#L88). Proposed solution:
```diff
public function execute(
\Magento\InventorySalesApi\Api\Data\SalesChannelInterface $salesChannel,
\Magento\Framework\Api\SearchCriteriaInterface $searchCriteria
): ExportStockSalableQtySearchResultInterface {
$stock = $this->getStockBySalesChannel->execute($salesChannel);
$productSearchResult = $this->getProducts($searchCriteria);
$items = $this->preciseExportStockProcessor->execute($productSearchResult->getItems(), $stock->getStockId());
/** @var ExportStockSalableQtySearchResultInterface $searchResult */
$searchResult = $this->exportStockSalableQtySearchResultFactory->create();
$searchResult->setSearchCriteria($productSearchResult->getSearchCriteria());
$searchResult->setItems($items);
- $searchResult->setTotalCount(count($items));
+ $searchResult->setTotalCount($productSearchResult->getTotalCount());

return $searchResult;
}
```

Start in InventoryExportStock/Model/ExportStockSalableQtyBySalesChannel.php, at execute() and the setTotalCount call identified in the issue. Reproduce the paginated GET request with the provided curl example, then verify that total_count represents all matching products rather than only the current page. Done means the response reports the full matching count while items remain paginated.

Written by the indexing model from the issue text.