Unify interface types and expose connect / disconnect methods

[tnull]

Based on #13.

So far the interface sometimes took Strings, &strs, or actual Rust
types. Moreover we sometimes took the arguments by reference and
sometimes not. In order to make the interface more uniform, we here take a step towards
the Rust types and taking arguments by reference.

Note that some of the affected parts are due to change in the future,
e.g., once we transition to using upstream's NetAddress for peer
addresses.

Also, by user request, we expose the capability to just connect a peer, which is useful for example when awaiting an incoming channel from an LSP.

[tnull]

Draft for now as still WIP.

[tnull]

Rebased on main after #13 has been merged.

[tnull]

Addressed feedback and rebased on main.

[tnull]

Rebased on main once more.

[jkczyz]

LGTM modulo a couple minor comments. Feel free to squash.

[tnull]

Squashed commits and removed a few more clones:

diff --git a/src/lib.rs b/src/lib.rs
index 1145aa0..8ce9bd6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -859,6 +859,6 @@ impl Node {
                let peer_info = PeerInfo { pubkey: node_id, address };

-               let con_peer_pubkey = peer_info.pubkey.clone();
-               let con_peer_addr = peer_info.address.clone();
+               let con_peer_pubkey = peer_info.pubkey;
+               let con_peer_addr = peer_info.address;
                let con_success = Arc::new(AtomicBool::new(false));
                let con_success_cloned = Arc::clone(&con_success);
@@ -879,10 +879,10 @@ impl Node {
                }

+               log_info!(self.logger, "Connected to peer {}@{}. ", peer_info.pubkey, peer_info.address,);
+
                if permanently {
-                       self.peer_store.add_peer(peer_info.clone())?;
+                       self.peer_store.add_peer(peer_info)?;
                }

-               log_info!(self.logger, "Connected to peer {}@{}. ", peer_info.pubkey, peer_info.address,);
-
                Ok(())
        }
@@ -939,6 +939,6 @@ impl Node {
                let peer_info = PeerInfo { pubkey: node_id, address };

-               let con_peer_pubkey = peer_info.pubkey.clone();
-               let con_peer_addr = peer_info.address.clone();
+               let con_peer_pubkey = peer_info.pubkey;
+               let con_peer_addr = peer_info.address;
                let con_success = Arc::new(AtomicBool::new(false));
                let con_success_cloned = Arc::clone(&con_success);
@@ -983,5 +983,4 @@ impl Node {
                ) {
                        Ok(_) => {
-                               self.peer_store.add_peer(peer_info.clone())?;
                                log_info!(
                                        self.logger,
@@ -989,4 +988,5 @@ impl Node {
                                        peer_info.pubkey
                                );
+                               self.peer_store.add_peer(peer_info)?;
                                Ok(())
                        }