Introduce stacked layout summary for runners list

What does this MR do and why?

This MR introduces the more compact layout for runners in a list that can be tested by users that enable the corresponding feature flags runner_list_stacked_layout and runner_list_stacked_layout_admin.

Implements the layout changes at #343133 (closed).

Check this comment for our reasoning to have feature flags here:

We will make the changes of moving the data in columns underneath the runner ID as it's own change, behind a feature flag.

Screenshots or screen recordings

before (FF off)	after (FF on)

How to set up and validate locally

Admin Runners:

1. Enable the new layout

   Feature.enable(:runner_list_stacked_layout_admin)

2. Visit admin runners page at Admin -> Runners (e.g. http://gdk.test:3000/admin/runners)
3. Check the layout
   1. If no runners are registered, follow the instructions in "Register instance runner"

Group Runners:

1. Enable the new layout

   Feature.enable(:runner_list_stacked_layout)

2. Go to Group -> CI/CD -> Runners
3. Check the layout
   1. If no runners are registered, follow the instructions in "Register group runner"

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #343133 (closed)