Add redis counter for viewing dashboard

What does this MR do and why?

• Adds a new redis counter to count every time the /*namespace_id/:project_id/-/analytics/dashboards(/*vueroute) route is invoked, with the optional vueroute parameter.
• This measures how many times a specific dashboard is visited, and excludes viewing the index list.

How to set up and validate locally

• Create a project that defines a product analytics dashboard.
• Visit a single dashboard and ensure that Gitlab::UsageDataCounters::ProductAnalyticsCounter.count is invoked once per pageview.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.