Remove Result for functions that are always Ok

[repi]

We had a bunch of redundant error handling in our renderer that was needed before this due to this crate returning Result<()> for a lot of functions that didn't have any failure conditions.

This wasn't very ergonomic to work with and it is not ideal to handle errors that can never happen, so this PR removes Result return values for vk-mem functions that returned void.

One could argue that more functions that return simple structs and values also here don't need to return it through a Result<value> if this crate always returns Ok on it, but chose to just do it for the simple void functions here which was the most obvious ones.

[repi]

As this changes the API, I think it would motivate/require a 0.3.0 release so users upgrade explicit to it and change their code that is using the functions in question