Make KeyHasher optional when the mutable-segment Bloom filter is disabled. - #170

Summary

• Make KeyHasher optional when MutableSegmentBloomFilterBitsPerItem is set to 0
• Skip key-hasher compatibility validation when the mutable-segment Bloom filter is disabled
• Improve missing-key-hasher validation messaging with guidance to configure a hasher or disable Bloom filtering
• Update docs to clarify when key hashers are required and how disabling Bloom filtering affects that requirement
• Add validation tests for missing hashers with Bloom filtering disabled
• Print a short profile-store benchmark run summary with runtime and peak memory
• Bump ZoneTree package version to 1.9.7.0