Test that max request body size is enforced for chunked encoding

HTTP does not specify a limit on request body size but allows implementations to enforce one to allow bounding of resource usage. When chunked encoding is used, the request body length is not known upfront and is only known incrementally as each chunk is received. Dropshot has a config option to set a maximum request body size but no test to verify that that limit is enforced when chunked encoding is used and a steady stream of chunks, each individually smaller than the limit, are received.

Start by locating the maximum request body size configuration and the chunked request handling. Add coverage for a steady stream of chunks where each chunk is below the limit but the cumulative body exceeds it, then run the relevant request-body tests and verify the request is rejected.