Added EventHandler and EventHandlerMut traits

[louisponet]

This changes the API to take in types that implement the EventHandler and EventHandlerMut traits rather than standard Fn.

This allows for functionality like:

use disrustor::{
    internal::SpinLoopWaitStrategy,
    *,
};

const MAX: i64 = 200i64;

struct Journal {
    pub i: u32,
    id: u32
}

impl Journal {
    fn new(id: u32) -> Self {
        Self {
            i: 0,
            id: id
        }
    }
}

impl EventHandler<u32> for Journal {
    fn handle_event(&mut self, event: &u32, seq: Sequence, eob: bool) {
        self.i = *event;
        println!(
            "journal: {}; msg: {}",
            self.id,
            self.i
        );
    }
}

fn main() {
    // let journal2 = std::cell::RefCell::new(Vec::<u32>::new()); // implemented somewhere else
    let (executor, producer) = DisrustorBuilder::with_ring_buffer(4096)
        .with_wait_strategy::<SpinLoopWaitStrategy>()
        .with_single_producer()
        .with_barrier(|b| {
            // journal + replication can happen in parallel
            b.handle_events(Journal::new(0));
            b.handle_events(Journal::new(1));
        })
        .build();

    let handle = executor.spawn();

    for i in 1..=MAX {
        std::thread::sleep_ms(1);
        producer.write([i], |d, _, _| {
            *d = i as u32;
        });
    }
    producer.drain();
    handle.join();
}

See #2

[codecov-commenter]

Codecov Report

Merging #3 (cd0ddbe) into master (5b280ab) will increase coverage by 0.0%.
The diff coverage is 73.0%.

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Impacted Files	Coverage Δ
src/prelude.rs	75.0% <ø> (ø)
src/dsl.rs	62.8% <50.0%> (ø)
src/lib.rs	90.3% <62.5%> (+0.3%)	⬆️
src/consumer.rs	100.0% <100.0%> (ø)

[sklose]

thanks for this PR @louisponet. I am going to merge this into a feature branch first so I can resolve the CI build issues. I will publish a new release once I am done.