Refactor labels management from HAML to Vue - table component

Summary

Part of &7139

Build a table.vue component in app/assets/javascripts/labels/components that renders the labels. It should fetch labels using GraphQL.

Improvements

1. Lazy load labels using GraphQL.
2. Allow for more flexibility when adding functionality to labels management
3. Remove HAML and jQuery
4. Use Pajamas compliant components

Risks

Miss existing functionality and introduce bugs

Involved components

• app/views/shared/_label.html.haml

Implementation plan

1. Use GlTable component to render table
2. Use GlLabel component to render label
3. Use GlDropdown to render actions dropdown
   • Edit, View issues with this label, View MRs with this label, View Epics with this label will be anchor tags

• Delete action will use app/assets/javascripts/vue_shared/components/delete_label_modal.vue

1. Use toggle_subscription action to toggle subscriptions