Add an http outcalls example

[mihailjianu1]

This showcases two ways of using the http outcalls feature in rust, and adds them to the icp ninja examples:

• A replicated http outcall to a constant, fairly deterministic service
• a non replicated outcall to a volatile service

In the case of the replicated http outcall, we also showcase the use of transform queries and how / why they help reach consensus.

[derlerd-dfinity]

I think we should mention here that one must be cautious with trusting such a response, as a malicious replica could return whatever it wanted. And maybe also that for practical purposes this usually means that one needs a way to verify the response out of band inside the canister, or to send out multiple such requests and only accept if enough responses agree.

[derlerd-dfinity]

Similarly, I'd also mention something along those lines in the readme.md.

[mihailjianu1]

Good points, I added some more comments both in the code and in the readme doc

[fxgst]

Is this supposed to replace the HTTP Get and HTTP Post examples? They seem quite overlapping

[letmejustputthishere]

i think there are some CI workflows missing
https://github.com/dfinity/examples/blob/master/ADDING_AN_EXAMPLE.md#ci

https://github.com/dfinity/examples/blob/master/NINJA_CONTRIBUTING.md#preparing-the-pr