Adding Upload & Delete to Project-level Secure Files UI

What does this MR do and why?

Adds the ability to upload and delete a Project-level Secure File from the UI. Adding a UI for https://docs.gitlab.com/ee/ci/secure_files/

Screenshots or screen recordings

How to set up and validate locally

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

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. A