Add featureFlags to GraphQL metadata field

What does this MR do and why?

From commit message:

Add featureFlags to GraphQL metadata field

• This can be used to see the enablement of a set of given feature flags.
• This is meant to replace the featureFlagEnabled field that was introduced in this MR. This field could only receive 1 flag at a time.
• This is marked alpha for now.

Changelog: added

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

How to set up and validate locally

1. Start GDK and sign in (the metadata field requires authentication).

2. Visit /-/graphql-explorer.

3. Try running a query like:

   query {
     metadata {
     version,
     featureFlags(names:["A","vscode_web_ide","web_ide_oauth","B","C","D","E","F","G","H","I","J","K","L"]) {
       enabled,
       name
     }
   }