Add x-gitlab-feature-category header to startup gql calls

• GraphQL calls return feature category and query file name to server
• Add labels from headers in web_transaction metrics
• Add x-gitlab-feature-category header to startup gql calls

What does this MR do and why?

This MR adds the x-gitlab-feature-category header to the Startup GraphQL calls so that we can accurately get the feature_category in our metrics surrounding these calls.

Screenshots

How to set up and validate locally

Apply the changes in this MR and the previous one !67800 (merged) locally

1. Startup the gdk locally and visit an issue show page
2. Visit /-/metrics
3. Search for gitlab_sql_duration_seconds_count{action="execute",controller="GraphqlController"
4. There shouldn't be any feature_category="not_owned" entries and only feature_category="issue_tracking"

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 #328535