[11.x] Enhanced typing for HigherOrderCollectionProxy

[Voltra]

HigherOrderCollectionProxy is a great feature of Laravel that helps reduce boilerplate code. Sadly there is no out-of-the-box decent auto-completion for it.

This PR makes HigherOrderCollectionProxy a templated type (as is Enumerable, Collection and EnumeratesValues) that aims to help IDEs provide auto-completion based on the collection's value type.

• What's been added: Nothing
• What's been modified: Docblocks to add and use the template type parameters
• Tests: none needed, no changes in code; auto-completion changes were tested in PHPStorm
• Hard breaking changes: none, no changes in code
• Soft breaking changes: Library authors that use HigherOrderCollectionProxy might want to update docblocks to include the correct template type parameters
• Room for improvement: As of now, this PR cannot properly type chains of HigherOrderCollectionProxy like $coll->keyBy->id->map->value->toArray()

[taylorotwell]

I think we have type tests - can you add one?

[Voltra]

I'll take a look at that

[taylorotwell]

There are a lot of unrelated changes here.

[Voltra]

My apologies, this should fix it