update parent_id at the very last

[ghost-not-in-the-shell]

Explain your changes: This PR moves the update to parent_id to the very end. The reason is that if berkeley_migration app crashed before migration finished. Then blocks with null parent_id would be considered as garbage and would be removed once migration being restarted.

Explain how you tested your changes: I've tested this change with umt data. Without this change, if we crash just after the parent_id being set, then the block would not be removed and those block would be considered valid and the corresponding blocks_user_commands table would not be populated after restart migration

Checklist:

• [ ] Dependency versions are unchanged

  • Notify Velocity team if dependencies must change in CI

• [ ] Modified the current draft of release notes with details on what is completed or incomplete within this project

• [ ] Document code purpose, how to use it

  • Mention expected invariants, implicit constraints

• [ ] Tests were added for the new behavior

  • Document test purpose, significance of failures
  • Test names should reflect their purpose

• [ ] All tests pass (CI will check this if you didn't)

• [ ] Serialized types are in stable-versioned modules

• [ ] Does this close issues? List them

• Closes #0000

[ghost-not-in-the-shell]

!ci-build-me

[ghost-not-in-the-shell]

!ci-build-me

[mrmr1993]

!approved-for-mainnet