fix: Resolve issue about the onShutDown function for Live entities

[Distractic]

Context

Currently, when using the method onShutDown of LiveEntity classes, the method only intercept the shutdown by events, not manually

Before

Manual

val message = // create message
val live = message.live()
live.onShutDown {
   // Never called
}
live.shutdown()

Event

val message = // create message
val live = message.live()
live.onShutDown {
   // Is called
}
message.delete()

Now

This issue is resolve with the attribut onShutDown present in AbstractLiveKordEntity

val message = // create message
val live = message.live()
live.onShutDown {
   // Is called
}

message.delete()
//or
live.shutdown()

[HopeBaron]

You shouldn't modify the behavior of the onShutdown function in this manner

here is a Mock

//implements CoroutineScope
interface LiveKordEntity : KordEntity, CoroutineScope


abstract class AbstractLiveKordEntity(dispatcher: CoroutineDispatcher) : LiveKordEntity {
     ...

    override val coroutineContext: CoroutineContext = dispatcher + SupervisorJob()

  
    override val events: Flow<Event>
        get() = kord.events
            .takeWhile { isActive // keeps trace of the scope's life-cycle }
            ...
   
}

// changed the on method to launched in the given LiveKordEntity's scope by default
inline fun <reified T : Event> LiveKordEntity.on(scope: CoroutineScope = this, noinline consumer: suspend (T) -> Unit) =
   ...
   

See #270, The proposed solution is to provide LiveEntitys with their own coroutine scope so they can manage their own lifecycle.
The user should be able to provide a dispatcher, that we will use for the entity to create a supervisor job that manages coroutines launched under it (children).

EDIT: You can safely remove the running state variable as we now use isActive instead.
The changes are not limited to this file, the change should affect any entity that extends the abstract class.