Feature: support randomize sequence

[unional]

Asynchronous call can come in different order.

Improve the validation logic to support randomize sequence as long as the resulting state is the same.

This requires the validation logic to construct a state machine from the recorded spec,
and accept any action sequence as long as the sequence produce the same state.

This will also give plugins to be more flexible and less rigid.

[unional]

This will be really hard to implement.