In this commit, we introduce unit tests for `ValidationAdmission`
webhook for the `ResourceInterpreterCustomization` resource. The
tests include:
- Tests how the webhook responds when decoding the request object fails.
- Tests how the webhook responds when it fails to retrieve list of objects from a namespace.
- Ensures that invalid `ResourceInterpreterCustomization` spec denies the admission.
- Confirms that valid `ResourceInterpreterCustomization` spec are allowed through without errors.
Signed-off-by: Mohamed Awnallah <mohamedmohey2352@gmail.com>