Fix total_gas_spent to exclude reservoir and use saturating arithmetic

Compute total_gas_spent as limit - remaining - reservoir in
build_result_gas to correctly exclude unused state gas. Use
saturating_sub in Gas::spent/total_gas_spent to prevent underflow.
Add std feature to ee-tests revm dependency.

Author: rakita

crates/ee-tests/Cargo.toml

@@ -16,7 +16,7 @@ workspace = true
 [dependencies]
 serde.workspace = true
 serde_json = { workspace = true, features = ["preserve_order"] }
-revm = { workspace = true, features = ["serde"] }
+revm = { workspace = true, features = ["serde", "std"] }
 op-revm = { workspace = true, features = ["serde"] }
 
 [features]

crates/handler/src/post_execution.rs

@@ -10,18 +10,20 @@ use primitives::{hardfork::SpecId, U256};
 
 /// Builds a [`ResultGas`] from the execution [`Gas`] struct and [`InitialAndFloorGas`].
 pub fn build_result_gas(gas: &Gas, init_and_floor_gas: InitialAndFloorGas) -> ResultGas {
-    // EIP-8037: tx_gas_used = tx.gas - gas_left - state_gas_left
-    // total_gas_spent = limit - remaining = tx.gas - gas_left
-    // Subtract reservoir to get the actual gas used (excluding unused state gas).
+    let state_gas = gas
+        .state_gas_spent()
+        .saturating_add(init_and_floor_gas.initial_state_gas)
+        .saturating_sub(init_and_floor_gas.eip7702_reservoir_refund);
+
     ResultGas::default()
-        .with_total_gas_spent(gas.total_gas_spent())
+        .with_total_gas_spent(
+            gas.limit()
+                .saturating_sub(gas.remaining())
+                .saturating_sub(gas.reservoir()),
+        )
         .with_refunded(gas.refunded() as u64)
         .with_floor_gas(init_and_floor_gas.floor_gas)
-        .with_state_gas_spent(
-            gas.state_gas_spent()
-                .saturating_add(init_and_floor_gas.initial_state_gas)
-                .saturating_sub(init_and_floor_gas.eip7702_reservoir_refund),
-        )
+        .with_state_gas_spent(state_gas)
 }
 
 /// Ensures minimum gas floor is spent according to EIP-7623.

crates/interpreter/src/gas.rs

@@ -112,13 +112,13 @@ impl Gas {
     Use [`Gas::total_gas_spent`] instead"
     )]
     pub const fn spent(&self) -> u64 {
-        self.limit - self.tracker.remaining()
+        self.limit.saturating_sub(self.tracker.remaining())
     }
 
     /// Returns the regular gas spent.
     #[inline]
     pub const fn total_gas_spent(&self) -> u64 {
-        self.limit - self.tracker.remaining()
+        self.limit.saturating_sub(self.tracker.remaining())
     }
 
     /// Returns the final amount of gas used by subtracting the refund from spent gas.