feat(engine): entitylist count performance for scalebyplayercount fn

[ultraviolet-jordan]

scaleByPlayerCount was created which calls into getTotalPlayers to get the current number of players in the World. The way getTotalPlayers is implemented is by manually counting the slots every time:

    get count(): number {
        let count: number = 0;
        for (const _ of this[Symbol.iterator]()) {
            count++;
        }
        return count;
    }

which the [Symbol.iterator] is a loop itself:

    *[Symbol.iterator](): ArrayIterator<T> {
        for (const index of this.ids) {
            if (index === -1) {
                continue;
            }
            const entity: T | undefined = this[index];
            if (typeof entity === 'undefined') {
                continue;
            }
            yield entity;
        }
    }

Since scaleByPlayerCount fn in World is used by removeNpc and removeObj, it is performing a double loop every time an npc or obj is removed from the world.

Refactor the count fn as so:

    get count(): number {
        return Math.max(this.length - this.free.size, 0);
    }

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::addobj2 64 adds an obj to every tile in a 64x64 square area, effectively adding and then removing 4096 objs.

The screenshots below are before & after when the 4096 objs despawn and shows the time taken.

Before:

After:

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I also added some extra info into the world cycle messages & refactored some other bits of code to simplify them.