Refactor Admin Deploy keys table to Vue

Summary

Follow up to #334874 (closed)

Currently the deploy keys table is rendered in HAML. This should be converted to Vue so we can use all of the GitLab UI components and it will be easier to build features in the future.

Improvements

• Can lazy load the deploy keys using the deploy_keys API endpoint
• Easier to add features to the table in the future
• Adds pagination
• Fixes N+1 issue

Risks

• Missed existing functionality

Involved components

• https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/views/admin/deploy_keys/index.html.haml

Implementation plan

1. Add feature flag check and mount element to app/views/admin/deploy_keys/index.html.haml
2. Create a table.vue component in app/assets/javascripts/admin/deploy_keys/components
   • GlTable will be used to render the table
   • GlModal will be used to confirm if a user wants to delete a key
   • GlPagination will be used for pagination
   • The data will be fetched via the deploy_keys API endpoint API endpoint
3. Export a function from app/assets/javascripts/admin/deploy_keys/index.js that mounts table.vue to the mount element in app/views/admin/deploy_keys/index.html.haml
4. Import and call that exported function in app/assets/javascripts/pages/admin/deploy_keys/index/index.js
5. Update feature specs spec/features/admin/admin_deploy_keys_spec.rb

Availability & Testing

Ensure package-and-qa job is run and the end-to-end tests are green before merging.