Greatly reduce load onto the Electrum backend

We achieve our optimizations in three ways:

1. Batching calls instead of making them individually.

To get access to the batch calls, we replace all our
calls to the HTTP interface with RPC calls.

2. Never directly make network calls based on function
calls on the wallet.

Instead, inquiring about the status of a script always
just returns information based on local data. With every
call, we check when we last refreshed the local data and
do so if the data is considered to be too old. This
interval is configurable.

3. Use electrum's notification feature to get updated
with the latest blockheight.

Co-authored-by: Thomas Eizinger <thomas@eizinger.io>
Co-authored-by: Rishab Sharma <rishflab@hotmail.com>

swap/tests/testutils/mod.rs

@@ -342,10 +342,6 @@ where
         .electrs
         .get_host_port(testutils::electrs::RPC_PORT)
         .expect("Could not map electrs rpc port");
-    let electrs_http_port = containers
-        .electrs
-        .get_host_port(testutils::electrs::HTTP_PORT)
-        .expect("Could not map electrs http port");
 
     let alice_seed = Seed::random().unwrap();
     let bob_seed = Seed::random().unwrap();
@@ -357,7 +353,6 @@ where
         alice_starting_balances.clone(),
         tempdir().unwrap().path(),
         electrs_rpc_port,
-        electrs_http_port,
         alice_seed,
         execution_params,
     )
@@ -380,7 +375,6 @@ where
         bob_starting_balances.clone(),
         tempdir().unwrap().path(),
         electrs_rpc_port,
-        electrs_http_port,
         bob_seed,
         execution_params,
     )
@@ -588,7 +582,6 @@ async fn init_test_wallets(
     starting_balances: StartingBalances,
     datadir: &Path,
     electrum_rpc_port: u16,
-    electrum_http_port: u16,
     seed: Seed,
     execution_params: ExecutionParams,
 ) -> (Arc<bitcoin::Wallet>, Arc<monero::Wallet>) {
@@ -608,14 +601,9 @@ async fn init_test_wallets(
         let input = format!("tcp://@localhost:{}", electrum_rpc_port);
         Url::parse(&input).unwrap()
     };
-    let electrum_http_url = {
-        let input = format!("http://@localhost:{}", electrum_http_port);
-        Url::parse(&input).unwrap()
-    };
 
     let btc_wallet = swap::bitcoin::Wallet::new(
         electrum_rpc_url,
-        electrum_http_url,
         bitcoin::Network::Regtest,
         datadir,
         seed.derive_extended_private_key(bitcoin::Network::Regtest)