[8.x] Split Collections Into A Separate Package

[taylorotwell]

This PR splits collections into a separate package while remaining backward compatible with older releases of Laravel.

This also necessitated the creation of a new illuminate/macroable package.

The Illuminate\Support collection classes were left in place and simply extend the new Illuminate\Collections classes where appropriate and override a few construction methods that use the self keyword. The Illuminate\Support\Arr class was treated the same way.

No existing tests needed to be changed.

[regiszanandrea]

@mathieutu #25421

[mattstauffer]

Yesssssssssss I am so happy!

[mathieutu]

YYOOOOOUUUUHHOOOUUU! 🎉

thx @regiszanandrea for the ping!

(After several years trying to push that, it only needed one tweet to @driesvints to got it! 🤣)

[nunomaduro]

I was trying to find something, but actually everything sounds good to me. 👍🏻

[xuandung38]

Nice

[olivernybroe]

Is the plan to remove the extended classes in the future? So there is no duplicate Collection and Macroable classes?

[driesvints]

@olivernybroe #32481

[taylorotwell]

@olivernybroe while technically yes I think it could be a year or two (or more) away. There is no maintenance overhead for us keeping them and it only inflicts pain on users by removing them.

[simonhamp]

Nice! Any chance that pagination could be added in now? A lot of love for this out there still: https://gist.github.com/simonhamp/549e8821946e2c40a617c85d2cf5af5e