This commit converts naked `new`s to `AK::try_make` and `AK::try_create`
wherever possible. If the called constructor is private, this can not be
done, so we instead now use the standard-defined and compiler-agnostic
`new (nothrow)`.
This changes Variant::visit() to forward the value returned by the
selected visitor invocation. By perfectly forwarding the returned value,
this allows for the visitor to return by value or reference.
Note that all provided visitors must return the same type - the compiler
will otherwise fail with the message: "inconsistent deduction for auto
return type".
This allows the construction of `Variant<int, int, int>`.
While this might not seem useful, it is very useful for making variants
that contain a series of member function pointers, which I plan to use
in LibGL for glGenLists() and co.
