Add E2E tests for permission based Project Secrets CRUD operations

Issue Link: #569617 (closed)

This MR adds comprehensive end-to-end (E2E) test coverage for the Project Secrets feature in GitLab's Secrets Manager. It implements automated tests to validate CRUD (Create, Read, Update, Delete) operations with permission-based access control across Roles, Users, and Groups.

Why is this needed?

The Secrets Manager feature requires thorough testing to ensure that:

• Secrets can be created, read, updated, and deleted correctly through the UI
• Permission-based access control works as expected for different permission types (Role-based, User-based, and Group-based)
• The UI interactions function properly across the entire secrets lifecycle
• Users without appropriate permissions are properly blocked from performing unauthorized actions

Test Coverage Summary

Operation	Test Case	Permission Type	User Role	Permission	Expected Result
Create	581636	Role-based	Maintainer	✅ Create	Secret created successfully
Create	581637	Role-based	Reporter	❌ No create	Permission error
Read	581639	Group-based	Reporter	✅ Read	Secret visible
Read	581640	Role-based	Reporter	❌ No read	Permission error
Update	581641	Role-based	Maintainer	✅ Update	Secret updated
Update	581642	Role-based	Reporter	❌ No update	Permission error
Delete	581643	Role-based	Maintainer	❌ No delete	Permission error
Delete	581644	User-based	Reporter	✅ Delete	Secret deleted