* feat: frontend instance
* no need to carry column length in `Column` proto
* add more tests
* rebase develop
* create a new variant with already provisioned RecordBatches in Output
* resolve code review comments
* new frontend instance does not connect datanode grpc
* add more tests
* add more tests
* rebase develop
Co-authored-by: luofucong <luofucong@greptime.com>
* SelectExpr: change to oneof expr
* Convert between Vec<u8> and SelectResult
* Chore: use encode_to_vec and decode, instead of encode_length_delimited_to_vec and decode_length_delimited
* Chore: move bitset into separate file
* Grpc select impl