Allocation encoding tests

[GalloDaSballo]

• Test Encoding and Decoding
• Verify that Encoding and Decoding are equivalent

The PR adds

    /// We expect this test to fail as the encoding is ambigous past u120
    function testFail_encoding_not_equal_reproducer() public {
        _receive_undo_compare(18371677541005923091065047412368542483005086202);
    }

Which shows that ambigous encoding is possible past u120

We should never have values of that size, however we would do best to enforce this by adding explicit checks