More resilient `MoneroWalletRpc` startup in the harness

Recently we se this problem on CI quite often:

```
 May 27 01:26:55.898  INFO testcontainers::core::wait_for_message: Found message after comparing 80 lines
May 27 01:27:00.858  INFO testcontainers::core::wait_for_message: Found message after comparing 2 lines
May 27 01:27:00.859  INFO monero_harness: Starting monerod: DQma_monerod
May 27 01:27:08.143  INFO testcontainers::core::wait_for_message: Found message after comparing 183 lines
May 27 01:27:08.204  INFO monero_harness: Starting miner wallet: miner
May 27 01:27:09.832  INFO testcontainers::core::wait_for_message: Found message after comparing 16 lines
May 27 01:27:12.261  INFO monero_harness: Starting wallet: alice
May 27 01:27:14.482  INFO testcontainers::core::wait_for_message: Found message after comparing 16 lines
thread 'alice_punishes_after_restart_if_bob_dead' panicked at 'called `Result::unwrap()` on an `Err` value: error sending request for url (http://127.0.0.1:49177/json_rpc): operation was canceled: connection closed before message completed
```

Given the message `connection closed before message completed` it is likely that the `monero-wallet-rpc` is not fully started yet.
Unfortunately we cannot wait to see a different message in the logs, because there are just no further deterministic messages after the one we are currently listening on.
to overcome this problem without extending testcontainers we introduce a retry mechanism when creating the wallet.

monero-harness/src/lib.rs

@@ -31,6 +31,7 @@ use std::time::Duration;
 use testcontainers::clients::Cli;
 use testcontainers::{Container, Docker, RunArgs};
 use tokio::time;
+use tokio::time::sleep;
 
 /// How often we mine a block.
 const BLOCK_TIME_SECS: u64 = 1;
@@ -251,12 +252,24 @@ impl<'c> MoneroWalletRpc {
             .get_host_port(RPC_PORT)
             .context("port not exposed")?;
 
-        // create new wallet
         let client = wallet::Client::localhost(wallet_rpc_port)?;
 
-        client
-            .create_wallet(name.to_owned(), "English".to_owned())
-            .await?;
+        // Create new wallet, the RPC sometimes has startup problems so we allow some
+        // retries
+        tokio::time::timeout(Duration::from_secs(10), async {
+            loop {
+                let result = client
+                    .create_wallet(name.to_owned(), "English".to_owned())
+                    .await;
+
+                match result {
+                    Ok(_) => { break; }
+                    Err(e) => { tracing::warn!("Monero wallet RPC emitted error {} - retrying to create wallet in 2 seconds...", e); }
+                }
+
+                sleep(Duration::from_secs(2)).await;
+            }
+        }).await.context("All retry attempts for creating a wallet exhausted")?;
 
         Ok((
             Self {