Convert SocketException to guzzle ConnectException

[luzrain]

Convert Amp\Http\Client\SocketException to guzzle GuzzleHttp\Exception\ConnectException

[kelunik]

I guess this is not always right, e.g. if a socket is closed while the request is sent, we likely don't want a ConnectException?

[luzrain]

Agreed, it might be better to handle this the same way as in CurlFactory.php, where only certain types of errors are converted to ConnectException, while all others are converted to RequestException.
But all raw SocketException should definitely be converted to either ConnectException or RequestException to be compatible with Guzzle, which always throws its own internal exceptions in such cases. Applications rely on these Guzzle exceptions, and they must remain consistent no matter what handler is used under the hood.

The only problem is that we cannot differentiate between SocketException cases. We need to add some form of differentiation to implement this properly.
See my related issue about this: amphp/http-client#379

[luzrain]

@kelunik
Could you please take another look at this PR?
I've made some update, now, timeout errors and DNS resolution errors (when possible to distinct them) are wrapped into ConnectException, while all other exceptions are wrapped into RequestException.

This behavior aligns with Guzzle default handlers, which also wrap exceptions into either ConnectException or RequestException.
For reference, see the implementations in CurlFactory and StreamHandler.