Patch transaction pool ordering zero tip (#2643)

## Description
Before this fix when tip is zero, transactions that use 30M have the
same priority as transactions with 1M gas. Now they are correctly
ordered

## Checklist
- [x] Breaking changes are clearly marked as such in the PR description
and changelog
- [x] New behavior is reflected in tests
- [x] [The specification](https://github.com/FuelLabs/fuel-specs/)
matches the implemented behavior (link update PR if changes are needed)

### Before requesting review
- [x] I have reviewed the code myself
- [x] I have created follow-up issues caused by this PR and linked them
here

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 - [2387](https://github.com/FuelLabs/fuel-core/pull/2387): Update description `tx-max-depth` flag.
 - [2630](https://github.com/FuelLabs/fuel-core/pull/2630): Removed some noisy `tracing::info!` logs
+- [2643](https://github.com/FuelLabs/fuel-core/pull/2643): Before this fix when tip is zero, transactions that use 30M have the same priority as transactions with 1M gas. Now they are correctly ordered.
 
 ### Added
 - [2553](https://github.com/FuelLabs/fuel-core/pull/2553): Scaffold global merkle root storage crate.

crates/services/txpool_v2/src/selection_algorithms/ratio_tip_gas.rs

@@ -109,7 +109,8 @@ where
 
     fn key(store_entry: &StorageData) -> Key {
         let transaction = &store_entry.transaction;
-        let tip_gas_ratio = RatioTipGas::new(transaction.tip(), transaction.max_gas());
+        let tip_gas_ratio =
+            RatioTipGas::new(transaction.tip().saturating_add(1), transaction.max_gas());
 
         Key {
             ratio: tip_gas_ratio,

crates/services/txpool_v2/src/tests/tests_pool.rs

@@ -710,6 +710,63 @@ fn get_sorted_out_tx_same_tips() {
     universe.assert_pool_integrity(&[]);
 }
 
+#[test]
+fn get_sorted_out_zero_tip() {
+    let mut universe = TestPoolUniverse::default();
+    universe.build_pool();
+
+    // Given
+    let gas_coin = universe.setup_coin().1;
+    let tx1 = TransactionBuilder::script(vec![], vec![])
+        .tip(10)
+        .max_fee_limit(0)
+        .script_gas_limit(GAS_LIMIT)
+        .add_input(gas_coin)
+        .finalize_as_transaction();
+
+    let (_, gas_coin) = universe.setup_coin();
+    let tx2 = TransactionBuilder::script(vec![], vec![])
+        .tip(10)
+        .max_fee_limit(0)
+        .script_gas_limit(GAS_LIMIT / 2)
+        .add_input(gas_coin)
+        .finalize_as_transaction();
+
+    let (_, gas_coin) = universe.setup_coin();
+    let tx3 = TransactionBuilder::script(vec![], vec![])
+        .tip(10)
+        .max_fee_limit(0)
+        .script_gas_limit(GAS_LIMIT / 4)
+        .add_input(gas_coin)
+        .finalize_as_transaction();
+
+    let tx1_id = tx1.id(&ChainId::default());
+    let tx2_id = tx2.id(&ChainId::default());
+    let tx3_id = tx3.id(&ChainId::default());
+
+    universe.verify_and_insert(tx1).unwrap();
+    universe.verify_and_insert(tx2).unwrap();
+    universe.verify_and_insert(tx3).unwrap();
+
+    // When
+    let txs = universe
+        .get_pool()
+        .write()
+        .extract_transactions_for_block(Constraints {
+            minimal_gas_price: 0,
+            max_gas: u64::MAX,
+            maximum_txs: u16::MAX,
+            maximum_block_size: u32::MAX,
+        });
+
+    // Then
+    assert_eq!(txs.len(), 3, "Should have 3 txs");
+    assert_eq!(txs[0].id(), tx3_id, "First should be tx3");
+    assert_eq!(txs[1].id(), tx2_id, "Second should be tx2");
+    assert_eq!(txs[2].id(), tx1_id, "Third should be tx1");
+    universe.assert_pool_integrity(&[]);
+}
+
 #[test]
 fn get_sorted_out_tx_profitable_ratios() {
     let mut universe = TestPoolUniverse::default();