feat(prot): synchronize network accounts [AC-1586]

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.

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Related to AC-1586