Show Pending Project Members on Pending Members Page

What does this MR do and why?

Show pending project members on Pending Members page.

Return pending project members in pending members graphql query.

Issue: #481984

Related issue: #464444 (closed), and related discussion: #464444 (comment 2086788378)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots

In the screenshots below, Chuckie Finster is a pending group member, while Stu Pickles is a pending project member.

Stu Pickles does not appear in the screenshot from master / Before, but does appear with the fix in this MR / After.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.