GCPtr can be null so it's not safe to assign it to a NonnullGCPtr unless
you know it to be non-null.
This exposed a number of wrong uses in LibWeb which had to be fixed as
part of this change.
Note that this still keeps the old behaviour of putting things in std by
default on serenity so the tools can be happy, but if USING_AK_GLOBALLY
is unset, AK behaves like a good citizen and doesn't try to put things
in the ::std namespace.
std::nothrow_t and its friends get to stay because I'm being told that
compilers assume things about them and I can't yeet them into a
different namespace...for now.
Even if the pointer value is const, the value they point to is not
necessarily const, so these functions should not add the qualifier.
This also removes the redundant non-const implementations of these
operators.
These are two new smart pointers that are really just raw pointers under
the hood. The initial benefit is all in the names, they allow us to
declare that we're pointing at something in the GC heap.
Later we may also find ways to add debugging logic or static analysis to
these types.
