Replace `int*` types with `uint*` where appropriate

[zanctor]

I suggest changing integer types to unsigned ones, where negative values are not expected (key/secret ID, nonce, versions, ParameterRange values, etc). This will double the range of possible values and potentially will make the process of random values generation easier.

[jorabin]

I have a feeling that signed integers were used because of there being no unsigned integer in Java and therefore ending up as a long in the Java protobuf binding.

[zanctor]

Ah, that makes sense. Closing the issue.