asio: Use internal ssl context and engine impl

Implement asio-ssl layer with three classes in asio::ssl::mbedtls:
* context -- replaces SSL_CTX, used mainly as a container to options,
certs, keys
* engine -- replaces SSL, implements the actual mbedtls operations
* bio -- implements openssl BIO specifically tailered to mbedtls and
its asio usage

Further updates:
* asio: Used shared_ptr<> for bio pairs
* asio: Add error checks to mbedtls-bio
* asio: Address potential ssl-context ownership issue
* asio: Address potential bio-engine ownership issue


* Original commit: espressif/esp-idf@d823106aa6

components/asio/port/src/asio_ssl_impl.cpp

@@ -0,0 +1,20 @@
+//
+// SPDX-FileCopyrightText: 2021 Espressif Systems (Shanghai) CO LTD
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+#include "asio/detail/config.hpp"
+#include "asio/ssl/detail/openssl_init.hpp"
+
+namespace asio {
+namespace ssl {
+namespace detail {
+
+// No OpenSSL in this implementation, instance is nullptr
+asio::detail::shared_ptr<openssl_init_base::do_init> openssl_init_base::instance()
+{
+    return nullptr;
+}
+
+} } } // namespace asio::ssl::detail