Turbopack: fix unhelpful error message when deleting folder fails (#81718)

### What?

Fixes the unhelpful error message:

```
[Error: No such file or directory (os error 2)] {
  code: 'GenericFailure'
}
```

Author: sokra

turbopack/crates/turbo-tasks-backend/src/database/db_versioning.rs

@@ -143,8 +143,11 @@ pub fn handle_db_versioning(
         }
     } else {
         path = base_path.join("temp");
-        // propagate errors: if this fails we may have stale files left over in the temp directory
-        remove_dir_all(&path)?;
+        if path.exists() {
+            // propagate errors: if this fails we may have stale files left over in the temp
+            // directory
+            remove_dir_all(&path)?;
+        }
     }
 
     Ok(path)

turbopack/crates/turbo-tasks-backend/src/kv_backing_storage.rs

@@ -166,9 +166,11 @@ impl<T: KeyValueDatabase> KeyValueDatabaseBackingStorage<T> {
     where
         T: Send + Sync + 'static,
     {
-        let startup_cache_state = check_db_invalidation_and_cleanup(&base_path)?;
-        let versioned_path = handle_db_versioning(&base_path, version_info, is_ci)?;
-        let database = (database)(versioned_path)?;
+        let startup_cache_state = check_db_invalidation_and_cleanup(&base_path)
+            .context("Failed to check database invalidation and cleanup")?;
+        let versioned_path = handle_db_versioning(&base_path, version_info, is_ci)
+            .context("Failed to handle database versioning")?;
+        let database = (database)(versioned_path).context("Failed to open database")?;
         let backing_storage = Self {
             inner: Arc::new_cyclic(
                 move |weak_inner: &Weak<KeyValueDatabaseBackingStorageInner<T>>| {