[11.x] Prevent bug (🐛) emoji on Collection/Dumpable dd method

[jessarcher]

When calling the dd method on a Collection or a class using the Dumpable trait, it currently outputs a second dump containing just the 🐛 emoji.

collect(['test'])->dd();

now()->dd();

The emoji is output by symfony/var-dumper when no arguments are passed to the dd function.

We see it with Collections and Dumpable classes because our dd methods call their own dump method, followed by an empty dd call.

A side effect is that the response will return a 200 instead of the usual 500 that the dd function returns when there is no previous output, because the first dump prevents dd from setting headers.

This PR addresses this by making the dd methods just call the dd function directly. The only downside I can see is if someone has customized their dump method, the dd method will no longer use it.

An alternative would be to continue calling the dump method, followed by an exit call. However, dd has some additional logic to set headers which we might want to reimplement.