feat: handle interface constructor registration

[romm]

By default, the mapper cannot instantiate an interface, as it does not
know which implementation to use. To do so, the MapperBuilder::infer()
method can be used, but it is cumbersome in most cases.

It is now also possible to register a constructor for an interface, in
the same way as for a class.

Because the mapper cannot automatically guess which implementation can
be used for an interface, it is not possible to use the Constructor
attribute, the MapperBuilder::registerConstructor() method must be
used instead.

In the example below, the mapper is taught how to instantiate an
implementation of UuidInterface from package ramsey/uuid:

(new \CuyZ\Valinor\MapperBuilder())
    ->registerConstructor(
        // The static method below has return type `UuidInterface`;
        // therefore, the mapper will build an instance of `Uuid` when
        // it needs to instantiate an implementation of `UuidInterface`.
        Ramsey\Uuid\Uuid::fromString(...)
    )
    ->mapper()
    ->map(
        Ramsey\Uuid\UuidInterface::class,
        '663bafbf-c3b5-4336-b27f-1796be8554e0'
    );

Fixes #217
Fixes #426