Update `Lily\Adapters\HTTP` so that cookies can be set on response headers

You can now add cookie associative arrays to
`$response['headers']['Set-Cookie'].
Shorten test by one line by using `ob_get_clean()`
Remove use of `Lily\Mock\Application` from `Lily\Test\Adapter\HTTP`
Remove use of mocks since we can use functions on their own now
Remove unused mocks
Remove use of Kint::shortenPath()

I'm not sure this functionality was really useful seeing as a full path
is usually more useful for me.