test(util): add unit tests for Atoi, ParseInt, ParseUint, and ParseFloat

[iamamirsalehi]

This pull request adds unit tests for the util package, specifically covering the following functions:

• Atoi
• ParseInt
• ParseUint
• ParseFloat

These tests validate both valid and invalid input cases to improve confidence in parsing logic and ensure correct error handling.

---

Test Coverage

The tests include:

• Basic positive and negative integer conversions
• Base-10, base-16, and base-36 parsing
• Unsigned integers and invalid (e.g., negative for uint)
• Float parsing, including special values like NaN
• Expected errors for malformed or invalid inputs

---

Motivation

Adding test coverage for utility parsing functions helps ensure correctness and guards against regressions in future changes. These are low-level helpers that are widely used internally, so ensuring their reliability is critical.

---

Checklist

• Unit tests added
• Follows repository conventions and naming
• No breaking changes introduced

[ndyakov]

Thank you @iamamirsalehi!

[ndyakov]

Looks good, thank you.

[iamamirsalehi]

Thanks for your review