Add support for data block hash index for column families with user-defined timestamps

[brennan913]

Summary

This patch consists of two changes.

• Strip user-defined timestamps (UDTs) from user keys during data block hash index creation and lookup. This ensures that the same key with distinct timestamps will hash to the same location, preventing Get()s from retrieving outdated values for a given timestamp. This operation is a noop for column families that don't use UDTs (i.e., for which ts_sz is 0).

• Add a new API, Comparator::KeysAreBytewiseComparableOtherThanTimestamp to enable use of BlockBasedTableOptions::kDataBlockBinaryAndHash for column families that use a timestamp-aware comparator with otherwise bytewise-comparable keys. This API provides semantics similar to the existing Comparator::CanKeysWithDifferentByteContentsBeEqual, except it only requires that the user key itself (not including timestamp) is bytwise comparable. This new API returns false by default, and should be overridden to return true for comparators that support these semantics. To use the data block hash index, a column family should use a comparator that overrides one of these APIs, and select BlockBasedTableOptions::kDataBlockBinaryAndHash.

Resolves issue #12100

Proposed Semantics

(Note that only one of KeysAreBytewiseComparableOtherThanTimestamp and CanKeysWithDifferentByteContentsBeEqual needs to be overriden)

Bytewise Comparable	Timestamp Enabled	CanKeysWithDifferentByteContentsBeEqual	KeysAreBytewiseComparableOtherThanTimestamp	Hash Index Enabled?
Yes	Yes	True	True	Yes
Yes	No	False	True	Yes
No	Yes	True	False	No
No	No	True	False	No

Test Plan

New unit test in db_with_timestamp_basic_test.cc based on repro from originally flagged issue
make clean && make all check -j$(nproc)
make jclean rocksdbjava jtest