Update CreateService::Base to handle tracked context

What does this MR do and why?

This MR adds tracked context support to manually created vulnerabilities by updating Vulnerabilities::CreateServiceBase to automatically associate vulnerability findings with the appropriate Security::ProjectTrackedContext .

Vulnerabilities::ManuallyCreateService (API) and Vulnerabilities::StarboardVulnerabilityCreateService (Starboard) both inherit from Vulnerabilities::CreateServiceBase.

Changes

• Updates Vulnerabilities::CreateServiceBase to accept and handle tracked context parameters
• Adds new GraphQL arguments projectTrackedContextName and projectTrackedContextType to the vulnerabilityCreate mutation
• Creates Security::ProjectTrackedContextsFinder to find tracked contexts by name, type, and state
• Automatically creates a default tracked context if none exists (Falls back to the project's default branch context when no specific context is provided)
• Set the project_tracked_context_id on associated vulnerability reads

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Related to #555972