Remove transaction retry functionality from Access RPC backend

[devin-ai-integration]

Remove transaction retry functionality from Access RPC backend

Closes: #7632

Summary

Removed the transaction retry mechanism from the Access RPC backend. This feature was designed to automatically retry transactions that were successfully sent to collection nodes but never finalized. According to the issue discussion, this feature has never been used on public Access nodes and contains technical debt that would need fixing before it could be safely deployed.

Changes:

• Deleted entire retrier package (engine/access/rpc/backend/transactions/retrier/)
• Removed RetryEnabled parameter from backend configuration
• Removed retry-enabled CLI flag from access node builder
• Removed RegisterTransaction and ProcessFinalizedBlockHeight methods from transactions backend
• Removed retry integration from RPC engine's finalization callback
• Updated both access and observer node builders
• Removed retry-related unit tests

Review & Testing Checklist for Human

• Verify production impact: Confirm that the --retry-enabled flag was never set to true in any production access node deployments (check node configs and deployment scripts)
• Check for missed references: Search the codebase for any remaining references to "retry" or "Retry" in the context of transaction handling that might have been missed
• Verify observer node change: Confirm the observer node builder change is correct and doesn't break observer node functionality
• Review removal completeness: Verify that removing ProcessFinalizedBlockHeight from the finalization callback doesn't break any other functionality that depended on it

Testing Plan

Since this feature was reportedly never enabled in production:

1. Run full CI suite to ensure no compilation or test failures
2. Deploy to a test environment and verify access nodes start up correctly
3. Submit test transactions and verify they are processed normally without the retry mechanism

Notes

• Link to Devin run: https://app.devin.ai/sessions/c951ccaf95434f2ea05da344eaa2a69c
• Requested by: [email protected] (@peterargue)
• The observer node builder update was initially missed but caught by CI and fixed in a follow-up commit
• All unit tests for the transactions package pass locally

[devin-ai-integration]

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
engine/access/rpc/engine.go	0.00%	1 Missing ⚠️

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[peterargue]

please also remove the mockery entry

[devin-ai-integration]

Done! Removed the retrier entry from .mockery.yaml in commit 59320d6.