Generate certificate with BoringSSL

[NghiaTranUIT]

Description

Currently, we dynamically generate remote certificates by executing some openssl CLI, which has a lot of cons:

• Bad performance since it forks a new process
• Rely on openssl from the user machine
• Difficult to generate programmatically

Since we're refactoring the Core v2 by Swift NIO, it's time to migrate to BoringSSL (https://github.com/apple/swift-nio-ssl)

Acceptance Criteria

• Generate programmatically the remote certificates
• Remove all dependencies on openssl
• Support custom Client/Server certificate

[NghiaTranUIT]

All done in #500