Lazy load autoloaded bucket components

[joeldrapper]

Autoloaded Ruby constants will not have corresponding proxy methods on Buckets, since these methods are defined on const_added. This PR solves that in two ways:

External access

Assuming a runtime environment where none of the constants are loaded by default — such as Rails with Zeitwerk during development — we use a bucket like this:

def view_template
  Components::Heading { "Hello" }
end

This call will autoload the Components module, but it will not autoload the Components::Heading module, since it’s just a method call on Components. How we handle this is the Components bucket catches the call with method_missing, and then tries to load the constant. If loading the constant is successful, it can call the newly defined Heading method on Components.

When included

If we include Components and then try to call Heading, again we will run into the same problem.

class MyComponent < Phlex::HTML
  include Components

  def view_template
    Heading { "Hello" }
  end
end

In this case, though, we can’t use method_missing. If you include Components and AnotherBucket and they both define a Heading component, you would expect AnotherBucket’s Heading component to take precedence over Components’ Heading component. If both buckets were using the method_missing technique, this precedence would be based on which bucket had their component autoloaded first.

So instead, when you include a bucket, we eager-load all that bucket’s components.