feature: merge PlaceOrder and SpotTrade; fix #145

[lispc]

This is a very big commit...

1. merge PlaceOrder with SpotTrade. So we no longer need a separate PlaceOrder L2 tx. It is very helpful for the real tps.
2. feature: implement strategy of overwrite order tree in state_manager #104 and feature: implement strategy of overwrite order tree in circuit #105 code complete. I will write tests later.

TODOs for circuits:

1. reuse UniversalChecker for Transfer / Withdraw / SpotTrade
2. test feature: implement strategy of overwrite order tree in state_manager #104 and feature: implement strategy of overwrite order tree in circuit #105
3. fix related Rust code
4. fix test/massive.ts