Previous implementation violated the RFC by having both the actual opcode and WS_FIN flag set for all fragments of a message.
Fixed by setting the opcode only for the first fragment and WS_FIN for the last one
Closes IDFGH-2938
Closes https://github.com/espressif/esp-idf/issues/4974
transport_ws can now be read multiple times in a row to read frames larger than the buffer.
Added reporting of total payload length and offset to the user in websocket_client.
Added local example test for long messages.
Closes IDF-1083
