Code cleanup and refactoring

...NLP/1. Data Collection/HNSW/CartesianDistanceMetric.swift

...tNLP/1. Data Collection/HNSW/CosineSimilarityMetric.swift

...ata Collection/HNSW/DeterministicDurableVectorIndex.swift

...a Collection/HNSW/DeterministicEphemeralVectorIndex.swift

...SwiftNLP/1. Data Collection/HNSW/MersenneTwisterRNG.swift

Sources/SwiftNLP/1. Data Collection/HNSW/SeedableRNG.swift

Sources/SwiftNLP/Resources/hnsw_testbasicexample.mmap

Sources/SwiftNLP/Resources/hnsw_testbasicqueryexample.mmap

Sources/SwiftNLP/Resources/hnsw_testsubreddit.mmap

...ests/1. Data Collection/HNSW/DurableHNSWCorpusTests.swift

...ts/1. Data Collection/HNSW/EphemeralHNSWCorpusTests.swift