net_http refactor (#17460)

* net_http: refactor net_http_new

The goal is to move calls to getaddrinfo() and connect() into
net_http_update(). This will make it possible for them to be replaced
with non-blocking alternatives later.

The net_http calling pattern right now allows callers to create the
http_connection_t, call net_http_new() which creates the http_t from
the http_connection_t, free the http_connection_t, and then start
calling net_http_update(). In order to preserve that, the http_t needs
to copy the values out of the http_connection_t on create. This also
preserves the http_connection_t values instead of freeing them, so the
connection would be able to be used later.

* net_http: implement dns cache

* net_http: separate out address resolution, connect, and request send

* net_http: perform getaddrinfo on separate thread

* net_http: implement basic connection pool

* net_http: refactor receive calls to read faster, do fewer reallocs

* net_http: build fix for platforms without SSL

* net_http: build fix for non-griffin builds

* net_http: build fix for non-threaded platforms