Native Builder: Define Snapshotter protocol (#491)

This PR defines the snapshotter protocol

```swift
    ///Mount a snapshot and all its previous layers
    func prepare(_ snapshot: Snapshot) async throws -> Snapshot

    /// Commit a snapshot, making it permanent.
    func commit(_ snapshot: Snapshot) async throws -> Snapshot

    /// Remove a snapshot from snapshot store
    func remove(_ snapshot: Snapshot) async throws
```

It updates executors to work with this new protocol

Sources/NativeBuilder/ContainerBuildExecutor/ExecutorError.swift

@@ -33,6 +33,7 @@ extension ExecutorError {
         case executionFailed
         case cancelled
         case invalidConfiguration
+        case unsupportedOperation
     }
 
     /// Represents the detailed context of an error that occurred during a build.