refactor: align error variant naming with hive and hbase operators

Rename ProductConfigTransform to GenerateProductConfig and fix
the display string casing to match the convention used across
all three dereference/validate extraction PRs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: adwk67

rust/operator-binary/src/controller/validate.rs

@@ -22,8 +22,8 @@ pub enum Error {
         source: stackable_operator::product_config_utils::Error,
     },
 
-    #[snafu(display("Failed to transform configs"))]
-    ProductConfigTransform {
+    #[snafu(display("failed to generate product config"))]
+    GenerateProductConfig {
         source: stackable_operator::product_config_utils::Error,
     },
 
@@ -89,7 +89,7 @@ pub fn validate_cluster(
     let role_config = transform_all_roles_to_config(airflow, &roles);
     let validated_role_config = validate_all_roles_and_groups_config(
         &dereferenced.resolved_product_image.product_version,
-        &role_config.context(ProductConfigTransformSnafu)?,
+        &role_config.context(GenerateProductConfigSnafu)?,
         product_config_manager,
         false,
         false,