Creates Vue component for trigger variables block in job log page

What does this MR do?

Creates Vue component for trigger variables block in job log page

Moves the following code into vue:

- if @build.trigger_request
  .build-widget.block
    %h4.title
      Trigger

    - if @build.trigger_request&.trigger&.short_token
      %p
        %span.build-light-text Token:
        #{@build.trigger_request.trigger.short_token}

    - if @build.trigger_variables.any?
      %p
        %button.btn.group.js-reveal-variables Reveal Variables

      %dl.js-build-variables.trigger-build-variables.hide
        - @build.trigger_variables.each do |trigger_variable|
          %dt.js-build-variable.trigger-build-variable= trigger_variable[:key]
          %dd.js-build-value.trigger-build-value= trigger_variable[:value]

https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/views/projects/jobs/_sidebar.html.haml#L32

What are the relevant issue numbers?

#50101 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides