Support automatically enable the consecutive cache of HashMap for HashAgg

[guo-shaoge]

Enhancement

Consecutive cache of HashMap: check code:

tiflash/dbms/src/Common/ColumnsHashingImpl.h

Line 212 in 93d7395

if constexpr (consecutive_keys_optimization)

It's useful when consecutive same key inserting into HashMap, because the cache avoid search HashMap.

But if NDV is big(a.k.a. all keys are different), the consecutive cache is useless and there will be extra copy of key.

So we should detect the NDV automatically and decide whether to use consecutive cache by the workload.