Add constructor for NodeContact

[KolbyML]

Description

I want to be able to construct the NodeContact object myself. As I want to impl From for NodeContact {} in our codebase, since for us Enr will always be present so having it behind a option is inconvenient

Notes & open questions

Change checklist

• Self-review
• Documentation updates if relevant
• Tests if relevant

@jxs @AgeManning @ackintosh ping for review

[AgeManning]

This PR seems fine to me, but it doesn't implement From.

Maybe I misunderstood the description?

[KolbyML]

This PR seems fine to me, but it doesn't implement From.

Maybe I misunderstood the description?

Oh I meant to say I am implementing

/// The contact info for a remote node.
#[derive(Clone, Debug)]
pub struct NodeContact {
    /// Key to use for communications with this node.
    pub public_key: CombinedPublicKey,
    /// The node's ENR.
    pub enr: Enr,
    /// The node's observed socket address.
    pub socket_addr: SocketAddr,
}

impl From<NodeContact> for Discv5NodeContact {
    fn from(value: NodeContact) -> Self {
        Discv5NodeContact::new(value.public_key, value.socket_addr, Some(value.enr))
    }
}

This in our codebase

[AgeManning]

Oh yeah, cool.