rename Amount::saturating_div into saturating_ratio (#4972)

## Motivation

The `Amount` can be multiplied by `u128` using `saturating_mul` but we
don't have an inverse operation. The existing `saturating_div` compute a
`u128` ratio between two amounts.

## Proposal

* rename `Amount::saturating_div` into `saturating_ratio`
* create a new `Amount::saturating_div` that takes a u128 similar to
`saturating_mul`

## Test Plan

CI

## Release Plan

- These changes should be backported to the latest `testnet` branch,
then
    - be released in a new SDK,

---------

Signed-off-by: Mathieu Baudet <[email protected]>
Co-authored-by: Andreas Fackler <[email protected]>

Author: ma2bd

linera-base/src/data_types.rs

@@ -463,6 +463,11 @@ macro_rules! impl_wrapped_number {
                 Ok(())
             }
 
+            /// Saturating division.
+            pub fn saturating_div(&self, other: $wrapped) -> Self {
+                Self(self.0.checked_div(other).unwrap_or($wrapped::MAX))
+            }
+
             /// Saturating multiplication.
             pub const fn saturating_mul(&self, other: $wrapped) -> Self {
                 Self(self.0.saturating_mul(other))
@@ -727,7 +732,7 @@ impl Amount {
     }
 
     /// Divides this by the other amount. If the other is 0, it returns `u128::MAX`.
-    pub fn saturating_div(self, other: Amount) -> u128 {
+    pub fn saturating_ratio(self, other: Amount) -> u128 {
         self.0.checked_div(other.0).unwrap_or(u128::MAX)
     }
 

linera-execution/src/policy.rs

@@ -407,7 +407,7 @@ impl ResourceControlPolicy {
     /// Returns how much fuel can be paid with the given balance.
     pub(crate) fn remaining_fuel(&self, balance: Amount, vm_runtime: VmRuntime) -> u64 {
         let fuel_unit = self.fuel_unit_price(vm_runtime);
-        u64::try_from(balance.saturating_div(fuel_unit)).unwrap_or(u64::MAX)
+        u64::try_from(balance.saturating_ratio(fuel_unit)).unwrap_or(u64::MAX)
     }
 
     pub fn check_blob_size(&self, content: &BlobContent) -> Result<(), ExecutionError> {