Add mutation to send runner usage analytics csv export

What does this MR do and why?

This MR adds the ability to generate a runner usage report that lists the top 500 projects that consumed runner minutes in the GitLab instance. The report is triggered by a new GraphQL and sent by email once ready. Note: Each commit is reviewable individually.

There will be a few follow-up MRs to improve the implementation:

• Allow configuring the number of projects, e.g. give me the top 10 projects using runner minutes, and aggregate the rest under Other
• Add audit event for operation

EE: true

Part of:

• #426561 (closed)
• #426562 (closed)

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Step	Screenshot
GraphQL mutation
E-mail
Generated CSV

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Start the clickhouse server ./clickhouse server

2. Run migrations bundle exec rake gitlab:clickhouse:migrate

3. Run mutation in http://gdk.test:3000/-/graphql-explorer:

   Query:

   mutation runnersExportUsage($input: RunnersExportUsageInput!) {
     runnersExportUsage(input: $input) {
       errors
     }
   }

   Query variables:

   {
     "input": {
     	"type": "INSTANCE_TYPE"
   	}
   }

   This will dispatch the worker asynchronously in Sidekiq, and the email should be available shortly in http://gdk.test:3000/rails/letter_opener/.

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.