asio: Basic SSL/TLS support in asio port for ESP platform

This port employs IDF port of OpenSSL for most common features, others
are discouraged or not supported. The port also introduces several stubs
for OpenSSL functions which ASIO needs to get compiled and linked.

Upstream ASIO supports WolfSSL as SSL/TLS stack, as well, which is
another option for SSL support in ASIO on ESP platform.


* Original commit: espressif/esp-idf@9459c0dd43

components/asio/CMakeLists.txt

@@ -1,3 +1,5 @@
 idf_component_register(SRCS "asio/asio/src/asio.cpp"
+                            "asio/asio/src/asio_ssl.cpp"
+                            "port/src/esp_asio_openssl_stubs.c"
                     INCLUDE_DIRS "asio/asio/include" "port/include"
-                    REQUIRES lwip)
+                    REQUIRES lwip openssl)