feat(hooks): Add project hook support for vulnerability events and branch filter strategy
This merge request adds support for two new webhook features in GitLab projects: vulnerability event notifications and branch filtering.
The changes include adding fields to track when security vulnerabilities are detected and to specify which branches should trigger the webhook (like "feature/*" to only monitor feature branches).
Four new integration tests were added to verify that project webhooks can be properly listed, retrieved, created, and updated with these new options. A helper function was also created to make it easier to set up test webhooks that automatically clean themselves up after tests complete.
The implementation extends the existing webhook functionality without breaking existing code, allowing developers to configure more precise webhook triggers for their GitLab projects.
Unblocks gitlab-org/terraform-provider-gitlab#6453 and gitlab-org/terraform-provider-gitlab#6478