feat: Make payload size limit a shardus config

[jintukumardas]

Added the payload size limit to the SnOpts type and updated the Sn function to use the provided limit.

[github-actions]

PR Reviewer Guide 🔍

⏱️ Estimated effort to review: 3 🔵🔵🔵⚪⚪

🧪 PR contains tests

🔒 No security concerns identified

⚡ Key issues to review Error Handling The error handling for the conversion of JavaScript number to Rust usize (line 420) is marked with a TODO but not implemented. This could lead to potential runtime errors if the conversion fails or is inaccurate. Error Handling The error message in line 102 does not provide details about what action to take or more context about the error, which might not be helpful for debugging.