Cookies should be set using "cookie" method instead of "header"

[imefisto]

Detailed description

Currently, if you set more than one cookie, the Set-Cookie header is sent once, with all the cookies comma separated, instead of sending one Set-Cookie for each cookie (like php function setcookie does).

Also there is what RFC 6265 says about it:

Origin servers SHOULD NOT fold multiple Set-Cookie header fields into
a single header field. The usual mechanism for folding HTTP headers
fields (i.e., as defined in [RFC2616]) might change the semantics of
the Set-Cookie header field because the %x2C (",") character is used
by Set-Cookie in a way that conflicts with such folding.

Context

If you need to set more than one cookie (my particular case is for using with cloudfront (aws)), the library will fold all the cookies in one single Set-Cookie header:

HTTP/1.1 200 OK
Set-Cookie: TestCookie1=Value1; TestCookie2=Value2; TestCookie3=Value3

While the right way would be:

HTTP/1.1 200 OK
Set-Cookie: TestCookie1=Value1
Set-Cookie: TestCookie2=Value2
Set-Cookie: TestCookie3=Value3

Possible implementation

I'm doing a PR request to handle this. The issue will be solved if the cookies are set using the "cookie" method from swoole server, instead of "header" method.