feat: Improve Easy RAG module with complete implementation

[jzb1006]

• Implement recursive document loading using Files.walkFileTree
• Implement glob pattern matching for file filtering
• Add comprehensive integration tests covering all loading scenarios
• Replace System.err.println with SLF4J Logger for proper logging
• Add detailed README documentation for the module
• Update parent POM version to 1.10.0-beta18-SNAPSHOT
• Add module to parent POM modules list
• Improve bean naming conventions (e.g., easyRagEmbeddingModel)

Features:

• Single file ingestion
• Non-recursive directory loading
• Recursive directory traversal
• Glob pattern file filtering (*.txt, *.md, etc.)
• Combination of recursion and glob patterns
• Conditional bean creation based on configuration

Test Coverage:

• Default bean creation without configuration
• Single file loading
• Directory loading (recursive and non-recursive)
• Glob pattern filtering
• Recursive glob pattern filtering
• Conditional ingestor creation

Issue

Closes #

Change

General checklist

• There are no breaking changes
• I have added unit and/or integration tests for my change
• The tests cover both positive and negative cases
• I have manually run all the unit and integration tests in the module I have added/changed, and they are all green

• I have added/updated the documentation
• I have added an example in the examples repo (only for "big" features)

Checklist for adding new Spring Boot starter

• I have added my new starter in the root pom.xml
• I have added a org.springframework.boot.autoconfigure.AutoConfiguration.imports file in the langchain4j-{integration}-spring-boot-starter/src/main/resources/META-INF/spring/ directory