Rename semantic indexes to search indexes

[mauvo]

Summary

• rename the Semantic indexes category and URLs to Search indexes, retaining redirects for existing links
• describe full-text indexes as lexical search and vector indexes as similarity search commonly used for semantic search
• distinguish explicitly queried search indexes from planner-selected search-performance indexes and update internal references
• align the SEARCH reference and index syntax overview with native vector and full-text index querying, including availability versions, scoring, filtering, pagination, and analyzers

Testing

• npm run build:preview

[neo4j-docops-agent]

This PR includes documentation updates
View the updated docs at https://neo4j-docs-cypher-1679.surge.sh

New pages:

• Search indexes

Updated pages:

• Additional Cypher features
• SEARCH
• Additions, deprecations, removals, and compatibility
• Vector functions
• Indexes
• Create indexes
• Search-performance indexes
• The impact of indexes on query performance
• Syntax