[Network] Verify originID against libp2p ID

[synzhu]

Today, the network layer does not verify the OriginID of a message, and it passes it directly to the engines.

There are many reasons that this is bad (opens the door to impersonation attacks), and now with unstaked nodes it is even more important to address this.

• The verification for staked nodes can be done by checking the OriginID against the From field of the raw message we get from libp2p. Given a Flow ID, we should be able to deduce the libp2p peer ID from the protocol state.
• For unstaked nodes, we will do the validation by comparing the given OriginID against the result of whatever deterministic libp2p ID -> Flow ID mapping we end up deciding on.
• For staked AN's, we will validate messages from the unstaked network inside the libp2p topic validator, but using the same method as above.

As a result, we may need to do some refactoring so that the network layer of the code is aware of whether it is a staked or unstaked network, so it can choose which verification logic to use from above. Alternatively, we can implement some message validators that do this validation.

We can write a test to ensure that this is all working:

• Start up two nodes, and from one of them send a message with an incorrect origin ID
• Check that this message is discarded by the receiving node.

[synzhu]

@huitseeker You can probably just implement the first bullet point out of the above. The second and third bullet points may not even be strictly necessary, since on the unstaked network the origin ID will be derived from the libp2p ID, so we could potentially just ignore whatever Origin ID value is inside the actual message.

[huitseeker]

This was actually not fixed in 1129, as we decided to defer this fix to a further PR.