feat(core): add user db

[vivianjeng]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (yarn build) was run locally in root directory and any changes were pushed
• Lint (yarn lint:fix) was run locally in root directory and any changes were pushed

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue Number: close #552

What is the new behavior?

• Config user state schema
• When calling getData, it updates the current user state db with the latest transitioned data
• latestTransitionedEpoch and latestTransitionedIndex can reuse the user state without searching from epoch 0

Does this introduce a breaking change?

• Yes
• No

Other information