test: add E2E tests for global rules (#3088)

[DSingh0304]

Why submit this pull request?

• Bugfix
• New feature provided
• Improve performance
• Backport patches

What changes will this PR take into?

This PR adds comprehensive E2E tests for the Global Rules resource, covering all CRUD operations and list page functionality.

Test Coverage (5 tests, all passing ✅):

• List page tests (global_rules.list.spec.ts) - 3 tests

  • Navigation to global rules page
  • Pagination using table controls
  • Pagination using URL search parameters

• CRUD with required fields (global_rules.crud-required-fields.spec.ts) - 1 test

  • Uses single plugin (response-rewrite)
  • Tests create and delete operations

• CRUD with all fields (global_rules.crud-all-fields.spec.ts) - 1 test

  • Uses multiple plugins (response-rewrite + cors)
  • Tests create and delete operations with complex configurations

Files Added:

• e2e/pom/global_rules.ts - Page Object Model with navigation helpers and assertions
• e2e/tests/global_rules.list.spec.ts - List page and pagination tests
• e2e/tests/global_rules.crud-required-fields.spec.ts - Single plugin CRUD tests
• e2e/tests/global_rules.crud-all-fields.spec.ts - Multiple plugins CRUD tests

Implementation Details:

• Uses Monaco editor for plugin JSON configuration (consistent with plugin_configs)
• Proper handling of delete confirmation dialogs
• Follows test patterns from routes, services, and plugin_metadata
• Proper cleanup with deleteAllGlobalRules helper
• Auto-generated ID capture and verification

Related issues

Closes #3088

Checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document? (N/A - E2E tests don't require documentation updates)
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first (Yes, only adds tests, no breaking changes)