lazily replaying prepared statements for session manager

Currently, we replay prepared statements as soon as `set session_states` executes. However, it may fail in some cases.
For example, in session A:
1. create table `t1`.
2. prepare a statement `stmt` from `select * from t1`.
3. drop the table `t1`.
Then migrate the session from A to B:
1. session B tries to replay the `PREPARE` statement, but it fails because table `t1` doesn't exist.
2. The session cannot be migrated because of the failure, and the client is disconnected.

However, there are 2 cases where the client doesn't need to be disconnected:
- the prepared statement `stmt` won't be executed anymore, because the user doesn't want it anymore.
- the session will recreate the table `t1` later, and then the `stmt` can be executed.

Except for dropping tables, there are other cases where this could happen:
- alter the table.
- drop the current db where the statement is prepared.
- update the privilege of the user after the statement is prepared.
- update the `sql_mode` after the statement is prepared.

So if replaying the prepared statement fails, we can save the encoded prepared statement and replay it when it is executed.