Closes AC-1586. Synchronizes network accounts:

- Adds a signature type, Internal, used for data entries created at genesis and for network account synchronization.
- Moves account update logic from UpdateKeyPage executor to `block.Executor.ProcessTransaction`.
- Pushes updates whenever `dn/oracle`, `dn/globals`, or `dn/network` are changed.
- Executes pushed key page updates via an internally produced transaction instead of directly.
- Creates BVN mirrors of `dn/oracle`, `dn/globals`, and `dn/network`.
- Unconditionally uses a simple initiator hash for synthetic transactions.

## Review Checklist

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## Merge Checklist

- [ ] CI is passing
- [ ] Merge conflicts are resolved
- [ ] All discussions are resolved

Related to AC-1586