Add editAdminUrl to Runner GraphQL API

What does this MR do and why?

This change adds a "edit_admin_url" field to the Runner entity in GraphQL to contain an edit runner page URL.

See the next MR to see usage of this field: !77682 (comment 804150600)

Screenshots or screen recordings

How to set up and validate locally

1. Visit the GraphiQL explorer (e.g. http://gdk.test:3000/-/graphql-explorer)
2. Input a query such as this:

query getRunners{
  runners{
    nodes {
      adminUrl
      editAdminUrl # New field
    }
  }
}

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 #347856 (closed)