PR: Add configurable tx confirmation strategy (Receipt / DAG inclusion) and wire Taraxa DAG tracking

Summary

This PR introduces a configurable confirmation strategy for outbound Ethereum transactions sent by the sequencer.

• Default behavior remains unchanged: wait for transaction receipt.
• New option: wait for Taraxa DAG inclusion up to a small, configurable depth before proceeding.

Additional changes:

• Adds a DAG inclusion tracking helper
• Integrates DAG confirmation into the send path
• Exposes new metrics for DAG success/failure
• Adds a Nix option to select the confirmation strategy per provider