feat: improve the TMS validation process (#4694)

Description
---
Adds a mutex on the TMS validation process to stop multiple validations running per time.

Motivation and Context
---
Validation on the transactions is run when the Base_node state changes, which is an automated event triggered when a base_node lags, a new block is received, or the wallet connects to a new base node. The other path for this is user triggered where the user manually triggers a validation. 

Triggering more than one validation at a time is a waste of resources and network traffic as the wallet now asks the same basenode for the same data more than once.

base_layer/wallet/src/transaction_service/error.rs

@@ -162,6 +162,8 @@ pub enum TransactionServiceError {
     ServiceError(String),
     #[error("Wallet Recovery in progress so Transaction Service Messaging Requests ignored")]
     WalletRecoveryInProgress,
+    #[error("Wallet Transaction Validation already in progress, request ignored")]
+    TransactionValidationInProgress,
     #[error("Connectivity error: {source}")]
     ConnectivityError {
         #[from]

base_layer/wallet/src/transaction_service/service.rs

@@ -74,7 +74,7 @@ use tari_script::{inputs, script, TariScript};
 use tari_service_framework::{reply_channel, reply_channel::Receiver};
 use tari_shutdown::ShutdownSignal;
 use tokio::{
-    sync::{mpsc, mpsc::Sender, oneshot},
+    sync::{mpsc, mpsc::Sender, oneshot, Mutex},
     task::JoinHandle,
 };
 
@@ -171,6 +171,7 @@ pub struct TransactionService<
     wallet_db: WalletDatabase<TWalletBackend>,
     base_node_service: BaseNodeServiceHandle,
     last_seen_tip_height: Option<u64>,
+    validation_in_progress: Arc<Mutex<()>>,
 }
 
 impl<
@@ -269,6 +270,7 @@ where
             base_node_service,
             wallet_db,
             last_seen_tip_height: None,
+            validation_in_progress: Arc::new(Mutex::new(())),
         }
     }
 
@@ -2199,8 +2201,15 @@ where
         );
 
         let mut base_node_watch = self.connectivity().get_current_base_node_watcher();
-
+        let validation_in_progress = self.validation_in_progress.clone();
         let join_handle = tokio::spawn(async move {
+            let mut _lock = validation_in_progress.try_lock().map_err(|_| {
+                debug!(
+                    target: LOG_TARGET,
+                    "Transaction Validation Protocol (Id: {}) spawned while a previous protocol was busy, ignored", id
+                );
+                TransactionServiceProtocolError::new(id, TransactionServiceError::TransactionValidationInProgress)
+            })?;
             let exec_fut = protocol.execute();
             tokio::pin!(exec_fut);
             loop {