Fetch project VSA medians from group VSA endpoint

What does this MR do?

Background

Currently project level VSA has a dedicated endpoint for retrievingthe VSA stages with various relevant information as well as summary metric data. In an effort to improve performance and also better align project and group level VSA, we can migrate the project level VSA to share the group level stage median endpoints.

This MR

This MR updates the project level VSA api requests for stage medians. With the group level VSA we have a dedicated endpoint for retrieving stage medians.

Screenshots or Screencasts (strongly suggested)

No visual changes

Testing instructions

1. Create a project within a group (make sure to initialize the project with a readme, or create it from a template)
2. Seed some test VSA data

$ VSA_SEED_PROJECT_ID=<project-id> VSA_ISSUE_COUNT=10 SEED_VSA=true FILTER=cycle_analytics rake db:seed_fu

1. Navigate to value stream analytics for the project, ie for a project named clean-vsa-project in group new-vsa-group it would be http://<gdk>/new-vsa-group/clean-vsa-project/-/value_stream_analytics (or find it in the left menu)

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #257830 (closed)