Deprecate empty AccessInterface and remove usages

I think #53 is a way to go

We could create more than one interface. For example:

/**
 * Access rules for a route.
 */
interface RouteAccessInterface {

	public function access(AccountInterface $account, RouteMatchInterface $route): AccessResultInterface;

}

Taking this a step further, in a routing file, if the class defined in _form implements this interface, then its ::access() method could be used automatically instead of having to be defined in _custom_access.

I updated the summary.

If we are not going to deprecate AccessInterface then the @todo in its code should be replaced with an explanation of when the interface should be used.

Before we get into patches, we need to discuss what to do.

Still a problem ...

Trying to figure out what the way forward here is.

#71 points to #53

But #53 points to #34 which is going to be quite disruptive as per #35

People would then also need to add defence when parameters aren't defined otherwise static analysis tooling such as phpstan will complain on higher levels.

I like the idea in #73, funnily enough core's CsrfAccessCheck already aliases AccessInterface as RoutingAccessInterface.