Fix inconsistent highlighting of already selected activity nav-links

What does this MR do?

• Remove edge case where user could deselect an activity nav-link (which seems to be returning all the events)
• Explicitly add an All tab to return all the events

Are there points in the code the reviewer needs to double check?

Shouldn't be

Why was this MR needed?

Resolves existing UI inconsistency

Screenshots (if relevant)

Before:

After:

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Tests
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

• Closes #21631 (closed)
• Closes #21452 (closed)