Purpose

This PR adds a discovery-time validation for @SuiteDisplayName in the Suite Engine.
If the annotation value is blank or whitespace-only, the engine now reports a DiscoveryIssue with WARNING severity.

Related issue

• Reject blank value for @SuiteDisplayName #4810

Key Changes

• SuiteTestDescriptor: invoke inspectSuiteDisplayName(...) during construction and report a warning when needed.
  (referred to DisplayNameUtils.validateAnnotation().)
• I initially considered using Preconditions.notBlank() to throw a PreconditionViolationException when the value contains only whitespace.
  However, to maintain backward compatibility, I decided that reporting a warning would be more appropriate than throwing an exception.

Definition of Done

• There are no TODOs left in the code
• Method preconditions are checked and documented in the method's Javadoc
• Coding conventions (e.g. for logging) have been followed
• Change is covered by automated tests including corner cases, errors, and exception handling
• Public API has Javadoc and @API annotations
• Change is documented in the User Guide and Release Notes