Use async unlink for file removal on upload

What does this MR do and why?

• Refactor using os.remove in the uploader listener and instead use the unlink function of anyio. This will ensure file removal happens asynchronously
• Try/catch this process so we don't silently fail
• Resolves #601 (closed)

How to set up and validate locally

• Upload a file that is greater than 100mb.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• Have you checked this doesn't interfere/conflict/duplicate someone elses work?
• Have you fully tested your changes?
• Have you resolved any lint issues?
• Have you assigned a reviewer?
• Have you applied correct labels?