task(34647) ContentletFactory migration to OS - ESContentletScroll API

[fabrizzio-dotCMS]

Proposed Changes

This PR implements the separation and abstraction of ESContentletScrollImpl to enable OpenSearch migration while maintaining backwards compatibility with the existing ElasticSearch implementation.

Key Changes:

• ✅ Created IndexContentletScroll interface - Common abstraction for both ElasticSearch and OpenSearch scroll implementations
• ✅ Extracted ESContentletScrollImpl - ElasticSearch-specific implementation maintaining existing functionality
• ✅ Added OSContentletScrollImpl - New OpenSearch implementation with equivalent scroll API functionality
• ✅ Updated ContentletFactory and related classes - Modified to use the new abstraction layer

Architecture Improvements

Before: Tightly Coupled Implementation

// Direct ES implementation in ContentletFactory
ESContentletScrollImpl scroll = new ESContentletScrollImpl(query, user, respectFrontendRoles, batchSize, sortBy);

After: Clean Abstraction Layer

// Factory method returns abstracted interface
IndexContentletScroll scroll = createScrollQuery(query, user, respectFrontendRoles, batchSize, sortBy);
// Implementation is determined at runtime based on configured search engine

Technical Details

New Interface: IndexContentletScroll

• Defines standard contract for scroll-based queries
• Supports both ElasticSearch and OpenSearch implementations
• Provides consistent API: nextBatch(), getTotalHits(), hasMoreResults(), close()
• Implements AutoCloseable for proper resource management

ElasticSearch Implementation (ESContentletScrollImpl)

• Made package-private - No longer exposed as public API
• Maintains all existing functionality - Zero behavioral changes
• Uses existing ElasticSearch client and search operations
• Preserves current configuration properties (ES_SCROLL_*)

OpenSearch Implementation (OSContentletScrollImpl)

• New OpenSearch-native implementation using OpenSearch Java client
• Equivalent functionality to ES implementation with OpenSearch API calls
• Uses OpenSearch-specific configuration properties (OS_SCROLL_*)
• Handles OpenSearch query translation and response processing

Migration Benefits

1. Zero Breaking Changes - Existing code continues to work unchanged
2. Runtime Engine Selection - Search engine determined by configuration
3. Consistent API - Same interface regardless of underlying engine
4. Isolated Implementations - ES and OS code separated and independently maintainable
5. Future-Proof Architecture - Easy to add additional search engines

I'll introduce the proper testing for this new impl when other relevant parts of the index mapping mechanism are in place.

This PR fixes: #34647

This PR fixes: #34647

[dsolistorres]

Really good set of changes, including the implementation for OpenSearch scrolling and the refactor to use a common abstraction for both OpenSearch and ElasticSearch