feat(gui, swap): allow change-address to be omitted and default to internal wallet (#68)

This PR:
- allows --change-address to be omitted and default to internal wallet address (https://github.com/comit-network/xmr-btc-swap/pull/1709). This is a change that is merged from upstream into our fork
- adds the necessary components for the tauri integration and the ui components to allow toggling between internal vs external refund address

Co-authored-by: binarybaron <86064887+binarybaron@users.noreply.github.com>
Co-authored-by: Einliterflasche <81313171+Einliterflasche@users.noreply.github.com>
Co-authored-by: Byron Hambly <byron@hambly.dev>

swap/src/cli/api/request.rs

@@ -44,8 +44,8 @@ pub trait Request {
 pub struct BuyXmrArgs {
     #[typeshare(serialized_as = "string")]
     pub seller: Multiaddr,
-    #[typeshare(serialized_as = "string")]
-    pub bitcoin_change_address: bitcoin::Address,
+    #[typeshare(serialized_as = "Option<string>")]
+    pub bitcoin_change_address: Option<bitcoin::Address>,
     #[typeshare(serialized_as = "string")]
     pub monero_receive_address: monero::Address,
 }
@@ -545,6 +545,21 @@ pub async fn buy_xmr(
             .as_ref()
             .expect("Could not find Bitcoin wallet"),
     );
+
+    let bitcoin_change_address = match bitcoin_change_address {
+        Some(addr) => addr,
+        None => {
+            let internal_wallet_address = bitcoin_wallet.new_address().await?;
+
+            tracing::info!(
+                internal_wallet_address=%internal_wallet_address,
+                "No --change-address supplied. Any change will be received to the internal wallet."
+            );
+
+            internal_wallet_address
+        }
+    };
+
     let monero_wallet = Arc::clone(
         context
             .monero_wallet