Option to release HTTP response body

[jcamiel]

See #5036 we can propose an option to release memory (mainly HTTP responses body in results) in case user doesn't need it (only --test and no report used for instance).

Option name ?

• --discard-body
• --no-save-body

[microtimber]

The related parameters I recommend are as follows:

• --discard-body Discard response body. If there have no asserts and reports about the response body, this option can free the memory that response body consumes earlier. Without this parameter, hurl will keep the body in memory before the program ends. It will consume a large amount of memory if the body is large, and parallel and repeated modes will increase memory usage.
• --truncate-body <BYTES> Truncates the request and response bodies that exceed this value. The default is -1 that indicates keeping the full body. A positive integer indicates the number of bytes of the body to retain. If there has no asserts on the response body or only asserts on body's heading, this option can help to reduse memory usage.