[4.0][Refactor][Ready] Rename CRUD::resource() to Route::crudResource()

[tabacitu]

In 3.0 we have a CRUD alias (pointing to CrudServiceProvider) that was registered for just one method - CRUD::resource(), which registers all the routes needed for a CRUD.

This PR:

• makes CRUD::resource() stop working;
• makes Route::crudResource() start working (doing the exact same thing);
• eliminates the CRUD alias;

Why:

• I don't think it makes sense to load this alias for just one method;
• There is a more intuitive and reasonable way to achieve the same thing, since the Route class in macroable;
• This opens up the possibility for us to use the CRUD alias for something else (not that we should, but we could);

Things we can do with the CRUD alias, since it would now be free to use:
(A) A services class (or helpers class), ex: CRUD::isCountable().
(B) A facade to the CrudPanel class (or currently running CrudPanel class). So that we can do:

// inside the ProductCrudController
CRUD::addField();
CRUD::addColumn();

// inside the views
CRUD::getEntry();

Instead of:

// inside the ProductCrudController
$this->crud->addField();
$this->crud->addColumn();

// inside the views
$crud->getEntry();

Obviously I think option B would be a better idea :-)

Thoughts? Feedback?

[tabacitu]

Let's close this in favour of #1937 - which does this, but also more. MUCH more :-)