3.x: fix Uri class usage

[LordSimal]

Http\Uri was dropped in cakephp/cakephp#16859

But now since we don't have a wrapper class holding the base info the DefaultUrlChecker needed to be updated and use the config values instead. I don't know if this is the correct way right now but it was the first that came to my mind.

[ADmad]

ServerRequest has the base as an attribute so instead of the Uri we can pass the request instance to the _getUrlFromRequest() method and check if $request->getAttribute('base') is non-empty.

[LordSimal]

So am I correct that the base attribute on the request has priority over the App.base config value?

[ndm2]

I don't think there should be a fallback, if the server request object has no base, then either the app has none, or the request object was created manually (not via the factory) or has the attribute unset, both of which indicates possible intent.

[ADmad]

The request's base attribute is set based on the App.base config, there's no need to check for it again and use it as fallback.