feat: Implement a shared Keycloak deployment and support modular auth configurations

[subhashkhileri]

JIRA : https://issues.redhat.com/browse/RHIDP-9752

Summary

• Add new Keycloak deployment helper for automated Keycloak setup on OpenShift
• Refactor RHDH deployment to support modular, pluggable authentication configurations
• Reorganize config files into auth-specific (auth/guest, auth/keycloak) and common directories

Changes

New Features

• Keycloak Deployment Helper: New module (src/deployment/keycloak/) for deploying and configuring Keycloak instances, including:
  • Helm-based deployment with configurable values
  • Realm, client, and user management
  • Integration with RHDH authentication

Refactoring

• Modular Auth Configs: RHDH config files reorganized to support different auth providers:
  • config/common/ - Shared configuration files
  • config/auth/guest/ - Guest authentication config
  • config/auth/keycloak/ - Keycloak/OIDC authentication config
• Enhanced kubernetes-client.ts with additional utilities
• Improved merge-yamls.ts for better config merging