Add CURLINFO_SIZE_DELIVERED and the size_delivered key to curl_getinfo() return types

[Amoifr]

Closes phpstan/phpstan#15371

PHP 8.6 adds CURLINFO_SIZE_DELIVERED and a size_delivered key to the array returned by curl_getinfo() (php/php-src@fd8eaaf15, libcurl >= 8.20.0).

• CURLINFO_SIZE_DELIVERED returns int|false, like the other options that need a recent libcurl (CURLINFO_POSTTRANSFER_TIME_T, CURLINFO_CONN_ID), following the convention from Update curl_getinfo() return types #4279.
• size_delivered: int is added right after size_download, in the order php-src fills the array. Like conn_id or used_proxy, it is not gated on the PHP version.