Highlight focused Design discussion in image markers

What does this MR do?

This MR implements the highlighting of the active discussion on the comments and the pin associated with this discussion. Both sidebar discussion and design pins are selectable with mouse click event now

When a certain discussion is selected

• The conversation will scroll and focus on that thread;
• The selected pin should be centered (or moved as close to the center of the screen as possible)
• Reduce the opacity of all other pins to 50% except for the selected one;
• Change the background color of the selected discussion on the sidebar to #F6FAFE.

The mouse cursor should not be a pointer when hovering over the conversation (except for the badge) but will be when hovering over a pin in the design.

If we click off the thread in the sidebar or click to drop a pin in the design, everything will reset to its unselected state.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Related issue: #33161 (closed)