feat(split): re-implement function split_replica_exec

[hycdong]

This pull request is re-implementing function split_replica_exec. During partition split, parent/child may want child/parent to execute another function, split_replica_exec is used for such function.

To simplify description, we assume that parent want child to execute function A. Parent replica calls function split_replica_exec directly, if child replica can be found on this replica_stub, child will execute function A, otherwise, parent will execute another function, usually is an error handler.

In current design, replica should execute functions in a same thread, whose id is calculated by its pid. However, split_replica_exec will let child replica execute function A in parent's thread, whose id is usually different from child's.

As a result, I re-implement split_replica_exec. Parent replica still calls function split_replica_exec directly, if child replica can be found on this replica_stub, replica_stub use tasking::enqueue to guarantee child replica execute function A in its own thread, and return ERR_OK, otherwise, return ERR_OBJECT_NOT_FOUND. Parent will execute the error handler if it got ERR_OBJECT_NOT_FOUND from split_replica_exec.

This pull request also updates unit tests and removes some useless cases.