Refactor runner active list component

What does this MR do and why?

This change splits the functionality of the runner active list in two so fetching and display logic are separate.

There are no user-facing changes.

Why this change?

We are adding a group runners variant of this dashboard at !151648 (merged), I plan to reuse the presentation component, and create a separate component with a smartQuery for the groups.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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How to set up and validate locally

1. We can seed data into our GDK, but the data seeded may not contain many running jobs, we can add this line to force more running jobs:

diff --git a/lib/gitlab/seeders/ci/runner/runner_fleet_pipeline_seeder.rb b/lib/gitlab/seeders/ci/runner/runner_fleet_pipeline_seeder.rb
index 2cd9afc5bdce..24aacfe01ecd 100644
--- a/lib/gitlab/seeders/ci/runner/runner_fleet_pipeline_seeder.rb
+++ b/lib/gitlab/seeders/ci/runner/runner_fleet_pipeline_seeder.rb
@@ -176,6 +176,7 @@ def create_build(pipeline, runner, job_status, index)
           end
 
           def random_pipeline_status
+            return 'running'
             if Random.rand(1..4) == 4
               %w[created pending canceled running].sample
             elsif Random.rand(1..3) == 1

1. Run bundle exec rake "gitlab:seed:runner_fleet" to generate a mock running jobs.
2. As an alternative, you can also run a few jobs in instance runners manually
3. Refresh the page to see the list.

Related to #424795 (closed)