coro-http: Add TLS support, do not send header when header is missing

[nilFinx]

Latter is another "me" thing, where some servers might not want to send anything after the request has been processed.

[Bilal2453]

#310 already does this, it is blocked by #341.

For the header thing, I don't think that's quite right, this will leak the connection. A response is required per spec, you can't just ignore it. If you really want, respond with an empty write manually which will force close it.

[nilFinx]

Unfortunately, I can't force close the connection - as that will, well, close the connection. I also can't return anything, as the client expects to see exactly HTTP/1.1 200 Connection Established\r\n\r\n before other operation in a loop happens, which does the TLS handshake.

And... oops. The PR is closed by pure accident. I'll reopen it, if you're fine with still getting it upstream.