Group/project members - migrate to one Vue app and `GlTabs`

Summary

Follow-up to #324675 (closed) and #324680 (closed)

Move to one Vue application that uses GlTabs to render the "Members", "Groups", "Invited", and "Access requests" tabs.

Improvements

Remove deprecated Bootstrap tabs in favor of GlTabs

Risks

Minimal, this is a well tested section of the codebase

Involved components

• app/assets/javascripts/members/components/app.vue
• Create tab_content.vue
• Update feature specs as some of them will now need the :js tag.
  • spec/features/projects/members/tabs_spec.rb
  • spec/features/groups/members/tabs_spec.rb

Implementation plan

• Move to one Vue mount point in app/views/groups/group_members/index.html.haml
• Update app/assets/javascripts/members/index.js to accept an object with keys as MEMBER_TYPE and value as the options.

{
  [MEMBER_TYPE.user]: {
    tableFields: ['account']
    ...
  },
  [MEMBER_TYPE.group]: {
    tableFields: ['account']
    ...
  }
}

• Update Vuex store to have 4 modules, MEMBER_TYPE.user, MEMBER_TYPE.group, MEMBER_TYPE.invite, and MEMBER_TYPE.accessRequest
• Create a new member_tabs.vue component. This component will render 4 GlTab elements with app/assets/javascripts/members/components/app.vue in the default slot. It will pass a namespace prop to app/assets/javascripts/members/components/app.vue.
• Update app/assets/javascripts/members/components/app.vue to accept a namespace prop. Use provide to provide the namespace prop to all subcomponents.