refactor: replace contract wrappers with native viem readContract

[alxdca]

Summary

• Replace contract-specific viem client decorators and read wrappers with native readContract calls using exported ABI/config objects.

Why / Context

• Contract-specific decorators duplicated encoding and transaction preparation behavior across ArbOwner, ArbAggregator, Rollup, and SequencerInbox integrations.
• Using viem's native contract reads and shared request helpers reduces the SDK's wrapper surface while preserving strongly typed function names and arguments.