Add sponsored tx num as metrics (MystenLabs#9779)

## Description 

As title

## Test Plan 

CI

---
If your changes are not user-facing and not a breaking change, you can
skip the following section. Otherwise, please indicate what changed, and
then add to the Release Notes section as highlighted during the release
process.

### Type of Change (Check all that apply)

- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes
Added sponsored tx number as metrics

crates/sui-core/src/authority.rs

@@ -165,6 +165,7 @@ pub struct AuthorityMetrics {
     total_cert_attempts: IntCounter,
     total_effects: IntCounter,
     pub shared_obj_tx: IntCounter,
+    sponsored_tx: IntCounter,
     tx_already_processed: IntCounter,
     num_input_objs: Histogram,
     num_shared_objects: Histogram,
@@ -251,6 +252,14 @@ impl AuthorityMetrics {
                 registry,
             )
             .unwrap(),
+
+            sponsored_tx: register_int_counter_with_registry!(
+                "num_sponsored_tx",
+                "Number of sponsored transactions",
+                registry,
+            )
+            .unwrap(),
+
             tx_already_processed: register_int_counter_with_registry!(
                 "num_tx_already_processed",
                 "Number of transaction orders already processed previously",
@@ -928,6 +937,10 @@ impl AuthorityState {
             self.metrics.shared_obj_tx.inc();
         }
 
+        if certificate.is_sponsored_tx() {
+            self.metrics.sponsored_tx.inc();
+        }
+
         self.metrics
             .num_input_objs
             .observe(input_object_count as f64);

crates/sui-types/src/messages.rs

@@ -1509,6 +1509,9 @@ pub trait TransactionDataAPI {
     fn is_change_epoch_tx(&self) -> bool;
     fn is_genesis_tx(&self) -> bool;
 
+    /// Check if the transaction is sponsored (namely gas owner != sender)
+    fn is_sponsored_tx(&self) -> bool;
+
     #[cfg(test)]
     fn sender_mut(&mut self) -> &mut SuiAddress;
 
@@ -1613,6 +1616,11 @@ impl TransactionDataAPI for TransactionDataV1 {
         self.check_sponsorship()
     }
 
+    /// Check if the transaction is sponsored (namely gas owner != sender)
+    fn is_sponsored_tx(&self) -> bool {
+        self.gas_owner() != self.sender
+    }
+
     /// Check if the transaction is compliant with sponsorship.
     fn check_sponsorship(&self) -> UserInputResult {
         // Not a sponsored transaction, nothing to check
@@ -1855,6 +1863,10 @@ impl<S> Envelope<SenderSignedData, S> {
     pub fn is_system_tx(&self) -> bool {
         self.data().intent_message().value.is_system_tx()
     }
+
+    pub fn is_sponsored_tx(&self) -> bool {
+        self.data().intent_message().value.is_sponsored_tx()
+    }
 }
 
 impl Transaction {