Fix premium project VSA author filter path

What does this MR do and why?

This MR fixes a bug similar to VSA: Group API URL malformed when filtering users (#396981 - closed), it ensures we:

• correctly set namespace type for project VSA that as missed in Set namespace type when bootstrapping VSA (!116206 - merged)
• fixes the isProjectNamespace getter
• sets the group name instead of group path for the project dropdown in group VSA

Note: there is no change in behaviour for FOSS project VSA

Screenshots or screen recordings

Before FOSS project	After FOSS Project
720-before-foss-project-vsa	720-foss-project-vsa

Before Premium project	After Premium Project
720-before-premium-project-vsa	720-premium-project-vsa

Before Group VSA	After Group VSA
720-before-group-vsa-filters	720-group-vsa-filters

How to set up and validate locally

1. Create a new project

2. Visit VSA for any project - you will see the FOSS view

3. Enable the vsa_group_and_project_parity feature flag

   Feature.enable(:vsa_group_and_project_parity)

4. Ensure you're on a GitLab Premium+ plan

5. Visit VSA for any project - you will see the "Create custom value stream" empty state

6. Create a custom value stream for the project - note the instructions are for groups, but its the same process

7. Test the filter bar

8. Repeat with VSA for any group

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 #382496 (closed)