Include task scheduling in core

[askvortsov1]

Fixes #2281

Changes proposed in this pull request:
Add a schedule method to the Console extender.

Reviewers should focus on:

• Should we add methods for each way to schedule? There's a LOT of options, so I think what I have here is simpler. On the other hand it's slightly less BC compatible, in case laravel decides to break something on its side. But I still think its way too many methods, and figuring out how to chain them is complicated.
• Turns out we need the helpers we literally just removed for this.... Given this it might make sense to add them back, but still discourage use just like we do now. Should we do this in the same PR?

Confirmed

• Frontend changes: tested on a local Flarum installation.
• Backend changes: tests are green (run composer test).

[askvortsov1]

When merging, if we decide to keep the helper changes done here, I'll split it into 2 commits:

1. the helper stuff
2. everything else

[imorland]

Checks out fine locally

[SychO9]

Should we add methods for each way to schedule? There's a LOT of options, so I think what I have here is simpler. On the other hand it's slightly less BC compatible, in case laravel decides to break something on its side. But I still think its way too many methods, and figuring out how to chain them is complicated.

We could make an adapter that reroutes method calls to the actual Event class, that way if laravel breaks something we'll have a BC layer, that said typehinting would be a problem, we could use a phpDoc block for that, but maintaining that can easily become a pain.

[askvortsov1]

Should we add methods for each way to schedule? There's a LOT of options, so I think what I have here is simpler. On the other hand it's slightly less BC compatible, in case laravel decides to break something on its side. But I still think its way too many methods, and figuring out how to chain them is complicated.

We could make an adapter that reroutes method calls to the actual Event class, that way if laravel breaks something we'll have a BC layer, that said typehinting would be a problem, we could use a phpDoc block for that, but maintaining that can easily become a pain.

I think it's safe to assume that if Laravel breaks this, they've probably broken other things, meaning that we'd only be including that upgrade in a major release.

[luceos]

Multiple class declarations in one file are really not done. It makes discoverability extremely hard. Either:

• move that class into its own file
• or use an anonymous class

[askvortsov1]

I keep forgetting anonymous classes exist. This is the perfect use case for one. I'll open a PR to clean this up, thanks!