Request body: flood detection for chunked request body

Request body: flood detection for chunked request body

Chunk sizes (including leading zeros), chunk extensions and trailers
of a chunked request body were not accounted, allowing a client to send
an unbounded amount of framing with little or no body data.

Now all received bytes are counted in rb->received and compared to
the body data, using the same flood detection as in HTTP/2 and HTTP/3.

Reported by jskoetsier.