Add WebFsIndexHelper for web and filesystem crawling

[marevol]

Major improvements:

• Extracted common filter processing logic into reusable methods (processFilters, addFailureExclusionFilters)
• Extracted crawler setup logic into dedicated methods (setupWebCrawler, setupFileCrawler)
• Extracted crawler execution logic into executeCrawlers method
• Reduced code duplication by ~250 lines

Code quality improvements:

• Fixed incorrect break statements (should be continue)
• Removed unused code (ComponentUtil.getFessConfig() call)
• Simplified AtomicBoolean usage in filter processing
• Improved error messages with config names
• Fixed issue where session IDs were added even for invalid configs

The doCrawl method is now much more readable and maintainable, going from ~380 lines to ~65 lines while preserving all functionality.