Enable canisters to make HTTP(S) requests

[janosroden]

Hi @yotam, forming a more expensive dual stack subnet would give the same guarantees I believe

HTTPS Outcalls to IPv4 Destinations - Update, and request for comments

Another way could be to form an ipv4 subnet (or more?) which cost a little bit more than the others. People can split their canister and put ipv4 site related logic to there and access the data with cross subnet calls. The capacity and performance of the subnet can be low, because canisters would be idle most of the time, aka wait either for the request or the response. Over time, as the transition to ipv6 continues, the demand for ipv4 subnet would decrease. Of course cross subnet calls are …