1. Support two checkpoint hooks saving final checkpoints in two difference folders
2. Remove the check of checkpoint hooks
3. Fix a incorrect modification in UT
4. Fix bug: Checkpoint.load_checkpoint has been moved out
5. Add UT for new style configuration
Link: https://code.alibaba-inc.com/Ali-MaaS/MaaS-lib/codereview/11630170
(cherry picked from commit 90af43f749)