feat(vector-set): add Vector Set support for Redis 8+

[bsbodden]

Implement all Vector Set commands with complete feature parity to redis-py:

Vector Set Commands:

• VSET.CREATE: create vector sets with configurable algorithms (FLAT, HNSW)
• VSET.ADD: add single or multiple vectors to a set
• VSET.DEL: delete vectors from a set
• VSET.GET: retrieve vectors by ID
• VSET.SEARCH: K-nearest neighbor (KNN) search
• VSET.RANGE: range queries with distance thresholds
• VSET.INFO: get vector set metadata and statistics
• VSET.SCAN: iterate through vectors in a set
• VSET.CARD: get cardinality (number of vectors)
• VSET.DROP: delete entire vector set

Algorithm Support:

• FLAT: brute-force exact search
• HNSW: hierarchical navigable small world graphs for approximate search
• Configurable parameters: dimension, distance metric, initial capacity
• Distance metrics: L2 (Euclidean), IP (Inner Product), COSINE

Features:

• Batch operations for efficient bulk inserts
• Flexible vector encoding (binary blob format)
• Metadata and statistics tracking
• Range queries with distance thresholds
• Efficient KNN search with configurable K
• Vector set scanning and iteration

Testing:

• Added 34 tests
• Test coverage for all vector set operations
• Algorithm-specific tests (FLAT, HNSW)
• Distance metric tests (L2, IP, COSINE)
• Batch operation tests
• Edge case and error condition tests

Documentation:

• Add vector_set_tutorial.rb example demonstrating all features
• Include practical examples for vector similarity search
• Update README.md with Vector Set documentation
• Update CHANGELOG.md with all new features

Infrastructure:

• Integrate Vector Set module into lib/redis/commands.rb
• Update .rubocop.yml to exclude generated files
• Update test/helper.rb for improved test infrastructure
• Requires Redis 8.0+ with vectorset module