[Berkeley] Fix fork config export

[georgeee]

Explain your changes:

• Use the correct value of staged ledger hash in the .ledger.hash field
• Do not inherit fields of genesis ledger (name, balances, num_accounts, hash)
• Make runtime_genesis_ledger more strict in accepting fork configs

Explain how you tested your changes:

• Re-run HF unit test
• Re-run last step of mainnet migration with updated hash
• Validate generated fork config manually

PR group:

• compatible: Fix fork config export #15462
• berkeley: [Berkeley] Fix fork config export #15464
• develop: [Develop] Fix fork config export #15465

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? None

[georgeee]

!ci-build-me

[emberian]

!ci-build-me

[georgeee]

!ci-build-me

[georgeee]

!ci-build-me

[deepthiskumar]

!approved-for-mainnet