fee: round up transaction weight to the nearest satoshi

[hieblmi]

lnd v0.19.2-beta introduced chainfee.FeeForWeightRoundUp which helps us fix #966.

[gemini-code-assist]

Summary of Changes

Hello @hieblmi, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on enhancing the accuracy and reliability of transaction fee calculations throughout the codebase. By switching to a fee estimation method that always rounds up to the nearest satoshi, I've mitigated the risk of transactions being rejected due to insufficient fees, which was a known issue. This ensures more robust and predictable on-chain operations.

Highlights

• Fee Calculation Improvement: I've updated all instances of FeeForWeight to FeeForWeightRoundUp across various modules, including instantout, liquidity, staticaddr, sweep, and sweepbatcher. This change ensures that transaction fees are consistently rounded up to the nearest satoshi.
• Bug Fix and Reliability: This modification directly addresses https://github.com/lightninglabs/loop/issues/966 by preventing scenarios where a rounded-down transaction weight could lead to undershooting the minimum relay fee, thus improving transaction reliability.
• Dependency Update Leverage: The change leverages the chainfee.FeeForWeightRoundUp function introduced in lnd v0.19.2-beta, indicating an update to or compatibility with a newer lnd version.

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[gemini-code-assist]

Code Review

This pull request addresses an important issue where transaction fees could be rounded down, potentially causing relay failures. The change to use FeeForWeightRoundUp across the codebase is a solid fix. The changes are consistent and correctly applied in all relevant files, including tests.

I've identified one area for improvement in sweepbatcher/sweep_batch.go where a block of code for manual fee rounding has become redundant due to this change. Removing it would improve code clarity.

Overall, this is a great and necessary change.