Cancel GitHub project imports - frontend

What does this MR do and why?

This MR exposes ability to cancel GitHub project imports

Related to #247325 (closed)

Screenshots or screen recordings

GitHub_import___GitLab

How to set up and validate locally

• Generate new GitHub token at https://github.com/settings/tokens
• open /import/github/new and use that token
• Start any import
• Cancel import

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.