Add feature flag to enable project level VSD

What does this MR do and why?

This MR adds a feature flag to enable / disable the project level Value streams dashboard. This MR:

• Adds a new feature flag to include/exclude the dashboard from the graphql response for the dashboard listing
• Updates related tests

Background

This dashboard is available from the shared analytics listing that is being developed by groupproduct analytics, the project level dashboard is still early on in development while groupoptimize has been focused on adding group level functionality. Therefore, in the meantime we should ensure the dashboard is only available opt-in via a feature flag until it stable and ready for wider use.

Screenshots or screen recordings

FF Disabled	FF Disabled - direct link	FF Enabled

How to set up and validate locally

1. Enable the project_analytics_dashboard_dynamic_vsd feature flag

   Feature.enable(:project_analytics_dashboard_dynamic_vsd)

2. Enable product analytics for a given project
3. From the project left sidebar, click the Analyze > Analytics dashboards link

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.

Related to #429541 (closed)