remove HAL implementation files for v3 and v4, and the build script

Software/MainBoard/rust/src/config.rs

@@ -88,9 +88,8 @@ pub enum BatteryBoardVersion {
 }
 #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Default)]
 pub enum BoardVersion {
-    #[default]
     Initial,
-    V3,
+    #[default]
     V4,
 }