Add previous exception to StreamException on socket accept failure

[hotfix31]

Hello! 👋

I encountered an issue while working with SSL/TLS sockets where error messages were not informative enough to diagnose configuration problems.

When stream_socket_accept() fails due to SSL/TLS configuration issues (e.g., inaccessible private key file), the original error message was lost and final users only saw: not accept on socket.

Now the exception includes the original error details: Could not accept on socket. (stream_socket_accept(): Unable to set private key file /certs/key.pem')`

This makes debugging SSL/TLS configuration issues much easier.

Thank you for maintaining this library! Let me know if you'd like any changes to this PR.

[sirn-se]

Thanks for contribution!
Very reasonable change, but I need to figure out why unit tests are failing. Code looks fine to me so need to dig around a bit.

[sirn-se]

Ok, it appears the missing cert file issue you're trying to provoke in the test does not cause exception until it has a stream accepted (which doesn't happen In the tests). So instead we end up with timeout exception in the test.

As I see it, there's no need to test specific errors that may occur, only that they are properly handled in the code.
So I would suggest;

1. Remove the entire testAcceptWithInvalidSslContextShowsPreviousException test case
2. On line 133 in the test, check that the exception (timeout) includes the error from lower-level error;

        $this->expectExceptionMessage('Could not accept on socket.');

to

         $this->expectExceptionMessage(
            'Could not accept on socket. (stream_socket_accept(): Accept failed: Operation timed out)'
        );

[hotfix31]

I processed all your feedback, I preferred to use a match on the exception message.

[sirn-se]

Released as v2.3.3. Thanks!