Add variables to policy drawer

What does this MR do and why?

This MR updates the policy drawer for execution policies to be more inline with the designs and adds CI customized variables into policy drawer. It also adds "automatically selected runners" when there are no tags defined.

Screenshots or screen recordings

With tags and variables	Without tags and with variables	Without both tags and variables

How to set up and validate locally

1. Upload a GitLab Ultimate license
2. Navigate to a project/group => Secure => Policies => New policy => Scan execution policy => create a policy with variables
3. View the policy in the policies list and verify the variables appear

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 #415053 (closed)