fix: Default authentication to kubernetes auth - #6735

Summary

Default Feast operator authentication to Kubernetes auth instead of no_auth, and add an explicit noAuth opt-out option for development/testing environments.

Changes

Default Kubernetes Authentication

• Change operator default from no_auth to kubernetes authentication
• Update util.go to apply default AuthzConfig with KubernetesAuthz
• Add warning log when running with no_auth
• Update enforcer.py to allow all authenticated users full access when no permissions are defined

noAuth CRD Option

• Add NoAuth field to AuthzConfig in both v1 and v1alpha1 API types
• Update CRD validation rules to allow noAuth as a third option alongside kubernetes and oidc
• Update repo_config.go to handle noAuth selection
• Update deepcopy generated code, CRD manifests, bundle, install.yaml, and docs

Test Updates

• Update operator unit tests for default auth behavior
• Update REST API integration test CRs with noAuth: true (these tests dont test auth)
• Update RBAC integration test expectations to match new enforcer behavior
• Add noAuth-specific tests

Test Plan

• Operator unit tests updated and passing
• CRD validation tests updated
• REST API test fixtures updated with explicit noAuth
• RBAC integration test expectations updated