API: Add tests for BinaryUtil

[uros-b]

Adds a unit test class for BinaryUtil, covering its public truncation helpers:

• truncateBinary - truncation to a shorter length, the fast path that returns the input buffer unchanged when the requested length already covers it, zero-length truncation, and the non-negative-length precondition.
• truncateBinaryUnsafe - the shared-backing-data view, and that the input buffer's position and limit are left unmodified.
• truncateBinaryMin - the ByteBuffer overload, and the Literal overload including its distinct branch that returns the input Literal unchanged when the length already covers the value.
• truncateBinaryMax - the ByteBuffer overload (incrementing the last byte to form the upper bound, and returning null when every byte overflows, all 0xFF), and the Literal overload including its propagation of that null result.

Test-only; no production code changes.

[uros-b]

Added some more tests

[uros-b]

@nastra Please review