### What problem does this PR solve?
- OpenTelemetry integration
- Checkpoint conformance tests
- State inspector API
- Callbacks
- A series of fault injection tests
- Pregel integration tests
### Type of change
- [x] Refactoring
### What problem does this PR solve?
- Tools management
- Pregel engine wrapper for better usage
- UT race
- Coding style
### Type of change
- [x] Refactoring
### What problem does this PR solve?
go-version of Pregel-based BSP engine
### Type of change
- [x] New Feature (non-breaking change which adds functionality)