Review necessity of serialization utility functions

[seemenkina]

The utility functions in rln/src/utils.rs are used across various serialization functions, and tests for them exist in rln/tests/protocol.rs. However, it’s unclear whether all of these functions are actually necessary.

Tasks:

• Analyze the usage of each function in utils.rs to determine if they are all needed.
• Check if any functionality is redundant or can be optimized.
• Consider simplifying or removing unused functions if possible.

Possible but maybe doesn't make sense

• Benchmark different serialization approaches to compare performance.
• Check with other team members to see what serialization methods they are using and whether these functions align with them.

Suggested changes

1. Update this function regarding current version of RLN. https://github.com/vacp2p/zerokit/blob/1930ca1610b85d59909fbbb6936ca042b6ebf1b8/rln/src/protocol.rs#L353

Example: https://github.com/vacp2p/zerokit/blob/1930ca1610b85d59909fbbb6936ca042b6ebf1b8/rln/src/public_api_tests.rs#L696-L706

2. Use this function inside test to avoid problem with serialisation https://github.com/vacp2p/zerokit/blob/1930ca1610b85d59909fbbb6936ca042b6ebf1b8/rln/src/protocol.rs#L371

One of place where need to replace: https://github.com/vacp2p/zerokit/blob/1930ca1610b85d59909fbbb6936ca042b6ebf1b8/rln/src/public_api_tests.rs#L724-L730

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Related issue: https://github.com/vacp2p/zerokit/issues/21