Declaring "needs" for a component with a Proc fails to compile

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Passing procs as parameters can be really helpful for named slots in Lucky components, as shown here:
https://www.youtube.com/watch?v=KoiKOD63tRQ

This episode originated from a snippet provided by @paulcsmith here:
https://gist.github.com/paulcsmith/01c1ced3e681de99d0ec343fdf57e2b7#gistcomment-3419386

Specifically, he wanted to be able to write something like:

```crystal
class MyCustomComponent < BaseComponent
needs user : User
needs some_content : ->
needs some_user_content : User->

def render
div do
some_content.call
some_user_content.call(user)
end
end
end
```

However, when using any more than one `needs` when any of them was a Proc, I kept getting a compile-time error of `Error: undefined macro method 'ProcNotation#types`. Switching to using `Proc` for the type worked, but Paul requested that an issue be opened to look into supporting the `->` syntax.

```crystal
class MyCustomComponent < BaseComponent
needs user : User
needs some_content : Proc(Void)
needs some_user_content : Proc(User)

def render
div do
some_content.call
some_user_content.call(user)
end
end
end
```

Start by compiling the minimal Crystal component example from the issue, first with arrow Proc syntax and then with Proc types. Trace the needs macro and the ProcNotation#types error to identify why multiple Proc needs fail; done means the arrow syntax compiles for both examples and the component can call each proc.

Written by the indexing model from the issue text.