Use DashMap to replace KeyedStateBackend in crates/fluxus-runtime/src/state.rs

[uran0sH]

In crates/fluxus-runtime/src/state.rs, we define a map struct:

#[derive(Default)]
pub struct KeyedStateBackend<K, V> {
    state: Arc<RwLock<HashMap<K, V>>>,
}

And the dashmap has a similar definition:

pub struct DashMap<K, V, S = RandomState> {
    shift: usize,
    shards: Box<[CachePadded<RwLock<HashMap<K, V>>>]>,
    hasher: S,
}

So we can replace it with dashmap

https://github.com/xacrimon/dashmap