Add inflation to epoch phases (#6787)

sdk/src/inflation.rs

@@ -42,6 +42,16 @@ impl Default for Inflation {
 }
 
 impl Inflation {
+    pub fn new_disabled() -> Self {
+        Self {
+            initial: 0.0,
+            terminal: 0.0,
+            taper: 0.0,
+            foundation: 0.0,
+            foundation_term: 0.0,
+            storage: 0.0,
+        }
+    }
     /// inflation rate at year
     pub fn total(&self, year: f64) -> f64 {
         let tapered = self.initial * ((1.0 - self.taper).powf(year));