fix: performance improvement and shuffling limited queries

[Sandros94]

The original shuffleArray and getRandomItems functions had a quadratic performance, mainly caused by splice in the loop, resulting in a $O(n^2)$ performance ($n$ being the number of items to shuffle).
With the these updated ones (credit to this awesome blog post about Fisher-Yates Shuffle) we get a much better linear performance of $O(n)$. Crucial when shuffling medium to big collections.

This also fixes the fact that when doing a limited query, the output would have still being sorted by ids in alphanumeric order.

Detailed Explanation

A slightly in-depth explanation on the performance improvement that this PR introduces (mainly discussed privately on Discord):

splice on its own has a performance of O(n), doing a for loop on an array has also a performance of O(n). The sum thus is O(n^2). Removing the usage of splice (thus editing the array inplace, without an additional array) makes us achieve O(n) performance in shuffleArray.

For getRandomItems its a similar story, the original one, using splice achieve a performance of a minimum of O(amount*n) and a maximum of O(n^2), but if we remove splice we go down to a minimum of O(amount) and a maximum of O(n). But since we only picked a random set, without truly shuffling it, we need to add a shuffleArray making it in the end a performance between O(amount^2) and a maximum of O(n^2)

[br41nslug]

As you may be able to guess this extension was not made with performance in mind (or production use for that matter). But i won't say no to a free performance improvement so will have a look at it later 🚀.

[Sandros94]

As you may be able to guess this extension was not made with performance in mind (or production use for that matter).

Oh I'm 100% aware of that! But since you mentioned it in directus/#3240 I wanted to contribute to this nice example. 😁

But i won't say no to a free performance improvement so will have a look at it later 🚀.

This is actually my first time placing my hands on a Directus extension, but I shouldn't have made a mess 😜

[Sandros94]

I've noticed a small mistake in getRandomItems, I'm fixing it right now.

[br41nslug]

Great addition, this shuffle algorithm is measurably more efficient 🚀