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
Previous version read all data to the buffer including header which reduced maximum payload read. This version uses a local array to receive header and reads payload bytes to the buffer
cherry-picked from db121a56e1
tcp_transport component used public header files such as 'transport.h', etc. which are too generic and might collide with user or user libraries headers
This change closes#2417
Four internal APIs `esp_http_client_connect()`, `http_client_prepare_first_line()`, `esp_http_client_request_send()` and
`esp_http_client_send_post_data()` API have been added for perfoming connection establishment (sync as well as async),
preparing first line, sending request and sending post data respectively.
In `transport_ssl`, `ssl_connect_async()` API has been added for establishing asynchronous connection.
added docs and tests for mqtt library, small fixes (removed warnings, option for custom outbox, websocket bug fixed for longer transports). refactored to use common tcp_transport component, support for CMake build system.
Closes#2108
