[Secrets Sync] enable access to Sync clients page for HVD clusters

[andaley]

:hammer_and_wrench: Description

• show sync clients in client count nav bar if there's a sync client history OR if the feature is able to be activated
• show sync charts on overview page if sync client history OR if the feature is activated

🧹 move client count nav bar to its own component

:camera_flash: Screenshots

:building_construction: How to Build and Test the Change

For OSS

• sync client charts and tabs should be hidden For HVD (most easily accomplished by pulling this down locally and hard-coding isHvdManaged = true in the flags service)
• sync client tab is shown
• charts are hidden unless there's a sync client history

[github-actions[bot]]

CI Results: failed :x:

[github-actions[bot]]

Build Results: Build failed for these jobs: ui:failure. Please refer to this workflow to learn more: https://github.com/hashicorp/vault/actions/runs/8942185273