Added a new API to WebSocket server to test provided socket descriptor if it belongs to active clients for this server and if websocket handshake has been performed
Closes https://github.com/espressif/esp-idf/issues/5602
Add logic to set `FIN` flag automatically for transmitted WS frames, but
if `fragmented` option set indicating an expert/manual mode, then the
`FIN` flag is set according to the `final` option.