[FEA] Require LFU strategy to ser score when lookup and (incremental) dump.

[shijieliu]

Is your feature request related to a problem? Please describe.
Support HKV's LFU evict_strategy in dynamicemb

Describe the solution you'd like
Introduce DynamicembScoreStrategy.FREQUENCE to support HKV's LFU evict_strategy.

Describe alternatives you've considered
N/A

Additional context
N/A

[shijieliu]

@jiashuy will update detailed work items.

[shijieliu]

@z52527 figured out how to implement this feature. will start this week

[shijieliu]

@z52527 is working on it.

[shijieliu]

resolved in #52