improve (HLS)ValidationIssue

### Description

comment I ran across in our current implementation:
// mamba validation issues have a poor interface. Best I can do is search in the description field when trying to find a specific issue in a list.

### Tasks

- [ ] change `public init(description: IssueDescription, severity: IssueSeverity)` to store the `IssueDescription` instead of just the description string
- [ ] change ` public init(description: String, severity: IssueSeverity)` to store the description as a `.undefined(String)` within `IssueDescription` enum
- [ ] change `description` attribute to an accessor of the string of the stored `IssueDescription`

### Open Questions

- Does this seem like the right approach IYO @dcoufal ?