fix(http1.1): set content length 0 when body is empty

[joelwurtz]

This force "Content-Length: 0" header when body is none (otherwise the client would consider this response as a Close Delimited body and would wait forever)

[fakeshadow]

The branch on extra status code check is good.

For adding content-lengh header we intentionally make the difference between "no body" and "empty sized body" so we keep the consistency across http/1, http/2, http/3.

In this case server should return with ResponseBody::body(Bytes::new()) or ResponseBody::bytes(Bytes::new()) rather than ResponseBody::empty()

The doc of Resonsebody::empty is wrong and cause this confusion due to refactor in rencent release. It shoud use be using the old ResponseBody::none as renference of doc

[fakeshadow]

#1390 would fix this issue. It works slightly different than previous comment as we cant break empty behavior with minor version bump so empty stays the same as doc comment stated and none method is added for the real no body use case