Use pub keyword instead of trivial getters and setters

[rikhuijzer]

I was unsure about whether using the pub keyword on struct fields, like for example,

struct Something {
    pub x: String
}

was a good idea or not. So to be on the safe-side, I decided to keep the fields private and use trivial getter and setter methods instead:

struct Something {
    pub x: String
}
impl Something {
    fn x(&self) -> String {
        self.x.clone()
    }
    fn set_x(&mut self, x: &str) {
        self.x = x;
    }
}

But I recently saw that Wasmtime makes some fields available via the public API. So if it is good enough for Wasmtime it's good enough for me. Let's rewrite all the trivial getters and setters in the library to pub fields.

[rikhuijzer]

The way to solve this would be to

1. Fork the xrcf repository
2. Open the codebase in an editor (preferably with rust language support built in, but it's not necessary)
3. Find a location in the codebase with trivial getters and setters
4. Make the field pub and remove the getters and setters
5. Run the code and look at the compiler errors
6. Fix all errors and make sure that cargo watch -x test succeeds again
7. (optional) find more places to remove getters and setters
8. Make pull request