[VSA] Dedicated Project VSA endpoints for stage medians, records and stage counts

Background

The following discussion from !65918 (merged) should be addressed:

• @ekigbo started a discussion: (+6 comments)

  Hey @ahegyi to use the group level stage median API request, i'm passing in the group path and also checking the cycle_analytics_for_groups license (so for FOSS we dont send api request to the group level), but this doesnt work for projects are not FOSS and fall under the user's namespace instead of a group.

  I tried passing the parent id/name instead, but stage median request fails. This wasnt a problem with the old endpoint since the median was embedded in the stats object.

  In the short term i could check if the groupPath is empty and use the old API request if it is, but it wouldnt be great if we still need to do that.

TODO

• Provide an endpoint to expose stage medians for project value streams
• Provide an endpoint to expose stage counts for project value streams
• Provide an endpoint to expose stage records (each event that occured) for project value streams
• All endpoints should:
  • Work for Projects in a group, projects in a personal namespace and FOSS projects (tbc)
  • Accept the same filters we use on a group level