audit: N-02 Code Clarity Suggestions

[Orland0x]

• When reading felt252 arrays from storage, the pointer offset is increased by the felt252 size, but the exit condition does not account for size. This behaves correctly because the size is actually 1, but we believe it would still be clearer to include it consistently.
• This hardcoded constant could use BoundedU8::max for readability.
• This hardcoded address could use zero for readability.
• This addition is unnecessary because it is equivalent to with_prefix = u256 {low: input, high: prefix} .
• The MerkleWhitelistVotingStrategy contract seems to unnecessarily split the user_params so they can be deserialized independently, instead of deserializing them together.
• The uint256_into_le_u64s function could return the components in a systematic order (i.e., most-significant 64-bit value to least-significant 64-bit value).
• This error message could be changed to Already finalized for consistency with the rest of the codebase.
• These two checks ([1] and [2]) can leverage the is_non_zero function.