feat: Package Provider Optionals

[martintc]

Still very much in draft. The idea is to refactor such that features of packages action return values wrapped in Option<>. Feature not implemented in package providers or incomplete can return None where comtrya will gracefully exit the action with a message that the feature is incomplete, not implemented or does not apply to the package manager.

[rawkode]

@martintc I think this might be easier to implement if you take a look at providers/mod.rs

pub trait PackageProvider {
    fn name(&self) -> &str;
    fn available(&self) -> bool;
    fn bootstrap(&self) -> Vec<Step>;
    fn has_repository(&self, package: &PackageVariant) -> bool;
    fn add_repository(&self, package: &PackageVariant) -> Vec<Step>;
    fn query(&self, package: &PackageVariant) -> Vec<String>;
    fn install(&self, package: &PackageVariant) -> Vec<Step>;
}

You'll see this trait. Below it, you could implement generic functions that log a "Does not implement" inside a impl PackageProvider block.

Let me know if that doesn't make sense and I'll provide an example.

[martintc]

@rawkode An example would be appreciated!