Object of class CurlHandle could not be converted to string on php 8

[AdiPP]

I got this error when curl session failed on PHP 8.

Error: Object of class CurlHandle could not be converted to string in /srv/app/vendor/lokielse/aliyun-open-api-sls/src/Requests/RequestCore.php:664
Stack trace:
#0 /srv/app/vendor/lokielse/aliyun-open-api-sls/src/Client.php(355): Aliyun\SLS\Requests\RequestCore->send_request()
#1 /srv/app/vendor/lokielse/aliyun-open-api-sls/src/Client.php(311): Aliyun\SLS\Client->getHttpResponse()
#2 /srv/app/vendor/lokielse/aliyun-open-api-sls/src/Client.php(289): Aliyun\SLS\Client->sendRequest()
#3 /srv/app/vendor/lokielse/aliyun-open-api-sls/src/Client.php(231): Aliyun\SLS\Client->send()

After some debugs, this is because you try to parse the CurlHandle object to string directly. Check this out:

// RequestCore.php
// ...
// The problem happen on `(string) $curl_handle`
if ($this->response === false) {
	throw new Exception('[RequestCoreException] cURL resource: ' . (string) $curl_handle . '; cURL error: ' . curl_error($curl_handle) . ' (' . curl_errno($curl_handle) . ')');
}
// ...

It works on PHP 5 through 7, but doesn't work on PHP 8 and caused a parsing error. So I make this PR #4 to update it.

Anyway, in case you still wanna use some info from your CurlHandle object for the exception message, consider using curl_getinfo. Based on PHP Doc, it comply with PHP 4 >= 4.0.4, PHP 5, PHP 7, and PHP 8.