feat: improve the override failure handling and message

[ryanzhang-oss]

Description of your changes

1. Be clear on what resource is the override apply failed
2. Add e2e on override key success and failure cases
3. Add e2e on cross namespace envelope failure cases
4. Add e2e on clusterAPI object

Fixes #

I have:

• Run make reviewable to ensure this PR is ready for review.

How has this code been tested

Special notes for your reviewer

[Arvindthiru]

We need to update this doc https://github.com/Azure/fleet/blob/main/docs/howtos/envelope-object.md#example-crp-status-where-resource-within-an-envelope-object-failed-to-apply

[Copilot]

Pull Request Overview

This PR improves the override failure handling and messaging while adding end-to-end tests to cover various override key scenarios and cross-namespace envelope cases.

• Updated error messages and logging in override rule application for both cluster and resource scopes.
• Added new e2e test contexts to validate proper behavior when using templated override rules and handling non‐existent cluster label keys.
• Minor refactors in controller and test files to improve clarity and consistency in resource extraction and error reporting.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/e2e/placement_ro_test.go	Added Placement assignment to ResourceOverride specs in tests.
pkg/controllers/workgenerator/override.go	Updated error messages and improved error handling in overrides.
pkg/controllers/workgenerator/controller.go	Simplified error messaging and renamed variables for clarity.
test/e2e/actuals_test.go	Improved error messages in work namespace removal test.
pkg/controllers/workgenerator/override_test.go	Minor improvements in error conversion in override tests.

Comments suppressed due to low confidence (2)

pkg/controllers/workgenerator/override.go:270

• Verify that constructing fullVariable via fmt.Sprintf correctly matches the intended substring in the input. The removal of dynamic index usage might cause incorrect replacements if multiple occurrences exist.

fullVariable := fmt.Sprintf("%s%s}", placementv1alpha1.OverrideClusterLabelKeyVariablePrefix, keyName)

pkg/controllers/workgenerator/controller.go:191

• [nitpick] Confirm that 'errorMessage' contains sufficient contextual details for debugging, as the previous formatted message provided additional clarity.

Message:            errorMessage,

[michaelawyu]

Hi Ryan! I am closing this PR as part of the CNCF repo migration process; please consider moving (re-creating) this PR in the new repo once the sync PR is merged. If there's any question/concern, please let me know. Thanks 🙏