Add security scan profile query type and resolver

What does this MR do and why?

Adds a new scanProfile query that allows fetching individual security scan profiles by their Global ID. This supports both default scan profiles (by scan type enum) and persisted scan profiles.

Changelog: added
EE: true

How to set up and validate locally

1. Sign in to your GDK as a developer in a group g.
2. Query using scan type-based global id:

query getSecurityScanProfile {
  securityScanProfile(id: "gid://gitlab/Security::ScanProfile/secret_detection") {
    name
    scanType
    gitlabRecommended
  }
}

2. Query with a non-existing scan type and verify resource not available error is raised:

query getSecurityScanProfile {
  securityScanProfile(id: "gid://gitlab/Security::ScanProfile/non_existing") {
    name
  }
}

3. Create and query a persisted profile:

    profile = Security::ScanProfile.create!(
      namespace_id: g.id,
      scan_type: :sast,
      name: 'Custom SAST',
      description: 'Custom config'
    )
    gid = profile.to_global_id.to_s

query getSecurityScanProfile {
  securityScanProfile(id: "gid://gitlab/Security::ScanProfile/<ID>") {
    name
    scanType
    gitlabRecommended
  }
}

MR acceptance checklist

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Related to [Backend] Add scan profile graphql field (#582869) • Gal Katz • 18.7