* feat(register_slot): add the RegstSlot

* feat(register_slot): update RegstSlot if

* feat(actor): update member of Actor to use RegstSlot

* fix(register_slot): fix the available_regst_desc_cnt init val

* refine(register_slot): rename PushBack/PopFront, FindTheRegstDescId to TryPushBack/TryPopFront, HasRegstDescId

* feat(regst_slot): rename ForEachCurRegstDeq/ForEachCurFrontRegst to ForEachRegstDeq/ForEachFrontRegst

* feat(regst_slot): add ForChosenRegstDeq/ForChosenFrontRegst, add CHECK empty in ForEachFrontRegst

* fix(register_slot): fix the CHECK empty

* feat: remove actual_writeable_regst_desc_id_ from Actor, add Naive/CustomizedProducedRegst

* fix(normal_model_update_actor): bug: not send customized regst to consumer when SendIntialModel

* fix(normal_forward_compute_actor): bug: not add kLoss/kAccuracy produced regst to NaiveProducedRegst

* fix(actor): UNIMPLEMENTED() for AsyncSendCustomizedProducedRegstMsgToConsumer

* fix(normal_forward_compute_actor): set const_buf_regst to nullptr when recv from consumers

* fix(actor): total_reading_data_regst_cnt, not total_reading_ctrl_regst_cnt

* refactor: update GetNaiveConsumedRegstDescName to GetNaiveOrCustomizedConsumedRegstDescName(same for Produced)

* feat: combine data_regst and ctrl_regst in Actor

* fix: fix bugs

* fix: fix bugs

* fix: remove .swp files and unused LOG

* feat: split Act and SendMsg (#1255)

* feat: split Act and SendMsg

* refine: rename HandleProduced/ConsumedDataRegst.. to HandleProduced/ConsumedNaiveDatRegst..

* fix(input_wise_comp_actor): bug: not set piece id

* fix(actor): potential bug: produced msg with no allowed actor still pop from queue

* refactor: mv some protected member function to private

* fix(actor): fix the condition about sending EORD msg

* refactor(input_wise_actor): use RegstSlot in InputWiseActor

* fix(copy_comm_net_actor): rename piece_id2regst_ctx to piece_id2regst_ctx_

* refactor: rename Name2RegstDescId to Name2RegstDescIds

* refactor(naive_actor): "override final" instead of only "final"

* refine(actor): little refine

* feat: update the return type of GetNaiveOrCustomizedNamesRegstDescName to enum class RegstNameType