BTreeKeySerializer: add random unit tests, fix UUID and some new methods
BTreeKeySerializer: optimize UUID
BTreeKeySerializer: add STRING_BYTE_ARRAY
BTreeKeySerializer: add keys split test
BTreeKeySerializer: long/int serializers can handle negative values, refactor docs accordingly
BTreeKeySerializer: Rename method
BTreeKeySerialier: remove method
BTreeKeySerialier: more work
BTreeMap: perf improvement in NodeSerializer
BTreeMap: fix string removal, move assertion outside of node ser/deser