Update Linked items widget count to use badge instead of icon

What does this MR do and why?

Linked items widget now uses badge to display the count instead of a link icon.

No popover is necessary to implement at this time.

Added aria label for accessibility.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

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Before	After

How to set up and validate locally

Check the new badge on any linked item widget within any work item.

Related to #482973 (closed)